Exhibit 99.1

ALLEGHANY CORPORATION

1411 Broadway, 34^th Floor

New York, NY 10018

ALLEGHANY CORPORATION REPORTS 2017 THIRD QUARTER RESULTS

NEW YORK, NY, November 2, 2017 – Alleghany Corporation (NYSE-Y) announced today its financial results for the three and nine months ended September 30, 2017. Highlights are listed below.

Weston Hicks, President and chief executive officer of Alleghany, stated, “Our results reflect large catastrophe losses in the third quarter of 2017, primarily arising from three hurricanes. We are pleased that our rigorous risk management protocols stood up to the test, and our (re)insurance subsidiaries are well-positioned to continue to serve their customers and markets. We continue to have a strong balance sheet and excellent liquidity. Despite these losses, Alleghany has been able to grow its book value per share by 3.3% in the first nine months of 2017.

1

Strong equity and modest bond market returns contributed to our book value growth in the quarter and helped offset the impact of the major catastrophe events. Although net investment income was down 13.2% in the third quarter of 2017, or $15.9 million, compared with net investment income in the third quarter of 2016, this was largely due to adverse results from collateralized reinsurance funds which were also hurt by the third quarter catastrophe events.”

Mr. Hicks continued, “Alleghany Capital continued to grow and reported solid results in the third quarter. Earnings before income taxes for the manufacturing and services businesses increased to $23.6 million compared with $16.7 million in the prior year third quarter. The manufacturing and services businesses also generated Adjusted EBITDA of $34.3 million in the third quarter of 2017, an increase of 34% over the $25.6 million of Adjusted EBITDA in the prior year third quarter. Oil & Gas losses before income taxes were ($6.7) million in the 2017 third quarter, roughly flat with the prior year third quarter.”

The following table summarizes results for the three and nine months ended September 30, 2017 and 2016:

The following table summarizes catastrophe loss impacts for the third quarter of 2017:

2

SEGMENT RESULTS

The following table summarizes the segment results for the three and nine months ended September 30, 2017 and 2016:

Reinsurance Segment

The increase in net premiums written in the third quarter of 2017 from the third quarter of 2016 is primarily related to reinstatement premiums written related to the significant catastrophe losses that occurred in the third quarter of 2017. The decrease in net premiums written in the first nine months of 2017 from the first nine months of 2016 primarily related to cancellations, non-renewals and reduced participations in certain international treaties, the impact of rate pressures and increased retentions by cedants and, to a lesser extent, the impact of changes in foreign currency exchange rates, partially offset by net premiums written in the third quarter of 2017 related to reinstatement premiums written.

The decrease at TransRe in net premiums written in the first nine months of 2017 from the first nine months of 2016 also reflects lower premiums related to a large whole account quota share treaty (the “Quota Share Treaty”). Premiums related to the Quota Share Treaty were $205.8 million and $199.4 million in the third quarter of 2017 and 2016, respectively, and $579.9 million and $624.2 million in the first nine months of 2017 and 2016, respectively. Premiums related to the Quota Share Treaty in the first nine months of 2016 reflect elevated premiums written in the first quarter of 2016 due to differences between initial premium estimates at contract inception, which were recorded in the fourth quarter of 2015, and actual data subsequently reported. As a consequence of this change in estimate, premiums written in the fourth quarter of 2015 were understated and premiums written in the first quarter of 2016 were correspondingly increased.

TransRe’s 2017 third quarter combined ratio was 149.8%, compared with 92.3% for the 2016 third quarter, and TransRe’s combined ratio for the first nine months of 2017 was 112.6%, compared with 93.9% for the first nine months of 2016. TransRe’s higher combined ratios and underwriting losses for the third quarter and first nine months of 2017, compared with its combined ratios and underwriting profits for the corresponding 2016 periods, primarily reflect an increase in catastrophe losses presented in the table summarizing catastrophe loss activity above. In addition, TransRe’s combined ratio in the first nine months of 2017 was impacted by $24.4 million of unfavorable prior accident year loss reserve development arising from the U.K. Ministry of Justice’s decision to significantly reduce the discount rate, referred to as the Ogden rate, used to calculate lump-sum bodily injury payouts in personal injury insurance claims in the U.K.

3

Insurance Segment

The increases in the insurance segment net premiums written in the third quarter and first nine months of 2017 from the corresponding 2016 periods reflect continued growth at PacificComp and CapSpecialty. For the third quarter and first nine months of 2017, PacificComp’s net premiums written increased by 11.9% and 17.6%, respectively, CapSpecialty’s net premiums written increased by 7.9% and 5.2%, respectively, and RSUI’s net premiums written increased by 1.5% and decreased by 1.5%, respectively.

The insurance segment’s combined ratio was 161.3% for the 2017 third quarter, compared with 86.8% for the 2016 third quarter, and the insurance segment’s combined ratio for the first nine months of 2017 was 111.1%, compared with 86.1% for the first nine months of 2016. The higher combined ratios and underwriting losses for the third quarter and first nine months of 2017, compared with its combined ratios and underwriting profits for the corresponding 2016 periods, primarily reflect the increase in catastrophe losses at RSUI, presented in the table summarizing catastrophe loss activity above.

Alleghany Capital

The following table summarizes earnings (losses) before income taxes and Adjusted EBITDA for Alleghany Capital for the three and nine months ended September 30, 2017 and 2016:

4

INVESTMENT PERFORMANCE

Alleghany reported net investment income for the third quarter and first nine months of 2017 of $104.7 million and $321.9 million, respectively, a decrease of 13.2% and 3.1%, respectively, from the corresponding 2016 periods, primarily related to losses incurred on our equity interests in collateralized retrocessional reinsurance related funds arising from significant catastrophe losses incurred in August and September 2017, and, for the nine-month period only, a $12.6 million charge in 2017 on our equity investment in Ares Management LLC (“Ares”). The charge on our equity investment in Ares reflects our share of a one-time payment recorded by Ares related to an acquisition by its affiliated entity. In connection with this acquisition, Ares agreed to make certain transaction support payments to the sellers of the acquired entity. Ares expects to receive future management fees derived from the assets under management of the acquired entity.

Financial statement total return³ on investments was 1.4% for the 2017 third quarter, compared with 1.1% for the 2016 third quarter. Year-to-date financial statement total return on investments was 4.9%.

OTHER FINANCIAL INFORMATION

As of September 30, 2017, Alleghany had 15,403,758 shares of its common stock outstanding, compared with 15,410,164 shares of its common stock outstanding as of December 31, 2016. During the third quarter and first nine months of 2017, Alleghany had repurchased an aggregate of 15,916 shares of its common stock in the open market for $8.5 million, at an average price per share of $537.14. As of September 30, 2017, Alleghany had $370.7 million remaining under its share repurchase authorization.

Additional Information

Concurrent with the issuance of today’s earnings press release, Alleghany has posted a financial supplement to its website, www.alleghany.com, containing additional schedules that provide further detail pertaining to Alleghany’s financial results.

Additional information regarding Alleghany’s 2017 third quarter and first nine months financial results, including management’s discussion and analysis of Alleghany’s financial condition and results of operations, is contained in Alleghany’s Quarterly Report on Form 10-Q for the period ended September 30, 2017 (the “Form 10-Q”), to be filed with the U.S. Securities and Exchange Commission (the “SEC”) on or about the date hereof. The Form 10-Q and the financial supplement will be available on Alleghany’s website at www.alleghany.com. The Form 10-Q will also be available on the SEC’s website at www.sec.gov. Readers are urged to review the Form 10-Q for a more complete discussion of Alleghany’s financial performance.

About Alleghany Corporation

Alleghany Corporation (NYSE-Y) creates value through owning and managing operating subsidiaries and investments, anchored by a core position in property and casualty reinsurance and insurance. Alleghany’s property and casualty subsidiaries include: Transatlantic Holdings, Inc. (referred to herein as “TransRe”), a leading global reinsurer; RSUI Group, Inc. (referred to herein as “RSUI”), a national underwriter of property and liability specialty insurance coverages; CapSpecialty, Inc. (referred to herein as “CapSpecialty”), an underwriter of commercial property, casualty and surety insurance coverages; and Pacific Compensation Corporation (referred to herein as “PacificComp”), an underwriter of workers’ compensation insurance, primarily in California. Alleghany’s subsidiary Alleghany Capital Corporation (referred to herein as “Alleghany Capital”) engages in and oversees strategic investments and acquisitions. Alleghany Capital’s investments include: (i) Bourn & Koch, Inc., a manufacturer/remanufacturer of specialty machine tools and supplier of replacement parts, accessories and services for a variety of cutting technologies; (ii) IPS-Integrated Project Services, LLC, a technical engineering-focused service provider focused on the global pharmaceutical and biotechnology industries; (iii) Jazwares, LLC, a global toy, entertainment and musical instrument company; (iv) R.C. Tway Company, LLC (dba and referred to herein as Kentucky Trailer), a manufacturer of custom trailers and truck bodies for the moving and storage industry and other markets; (v) Stranded Oil Resources Corporation, an exploration and production company focused on enhanced oil recovery; and (vi) WWSC Holdings, LLC, a structural steel fabricator and erector. For additional information about Alleghany Capital Corporation, please visit www.alleghanycc.com.

³ As calculated in Alleghany’s financial supplement.

5

Non-GAAP Financial Measures

Throughout this press release, Alleghany’s results of operations have been presented in the way that Alleghany believes will be the most meaningful and useful to investors, analysts, rating agencies and others who use financial information in evaluating the performance of Alleghany. This presentation includes the use of underwriting profit, operating earnings per diluted share and Adjusted EBITDA, which are “non-GAAP financial measures.” The presentation of these financial measures is not intended to be considered in isolation or as a substitute for, or superior to, financial information prepared and presented in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). Also note that these measures may be different from non-GAAP financial measures used by other companies, limiting their usefulness for comparison purposes. A discussion of our calculation and use of these financial measures is provided below.

Underwriting profit represents net premiums earned less net loss and loss adjustment expenses and commissions, brokerage and other underwriting expenses, all as determined in accordance with U.S. GAAP and does not include net investment income, net realized capital gains, other than temporary impairment losses, other income, other operating expenses, corporate administration, amortization of intangible assets and interest expense. Alleghany consistently uses underwriting profit as a supplement to earnings before income taxes, the most comparable U.S. GAAP financial measure, to evaluate the performance of its segments and believes that underwriting profit provides useful additional information to investors because it highlights net earnings attributable to a segment’s underwriting performance. Earnings before income taxes may show a profit despite an underlying underwriting loss; and when underwriting losses persist over extended periods, a reinsurance or an insurance company’s ability to continue as an ongoing concern may be at risk.

A reconciliation of underwriting profit to earnings before income taxes is presented below.     

Operating earnings per diluted share represents earnings per diluted share excluding (on an after-tax basis) net realized capital gains and other than temporary impairment losses, all as determined in accordance with U.S. GAAP. Alleghany uses operating earnings per diluted share as a supplement to diluted earnings per share, the most comparable U.S. GAAP financial measure, to provide useful additional information to investors by highlighting earnings per diluted share attributable to its performance exclusive of realized capital gains or losses and impairments. A reconciliation of operating earnings per diluted share to diluted earnings per share is presented below.

6

Adjusted earnings before interest, taxes, depreciation and amortization (“Adjusted EBITDA”) is a non-GAAP financial measure for our non-insurance operating subsidiaries and investments held by Alleghany Capital. Adjusted EBITDA represents other revenue less certain other expenses and does not include: (i) depreciation expense (a component of other operating expenses); (ii) amortization of intangible assets; (iii) interest expense; (iv) net realized capital gains; (v) other than temporary impairment losses; and (vi) income taxes. Because Adjusted EBITDA excludes interest expense, income taxes, net realized capital gains, other than temporary impairment losses, depreciation and amortization, it provides an indication of economic performance that is not affected by levels of debt, interest rates, effective tax rates or levels of depreciation and amortization resulting from acquisition accounting. Alleghany uses Adjusted EBITDA as a supplement to earnings before income taxes, the most comparable U.S. GAAP financial measure, to evaluate the performance of certain non-insurance operating subsidiaries and investments. A reconciliation of Adjusted EBITDA to earnings before income taxes is presented above in “Segment Results-Alleghany Capital.”

# # #

Forward-looking Statements

This release contains disclosures which may be deemed to be “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements may be identified by the use of words such as “may,” “will,” “expect,” “project,” “estimate,” “anticipate,” “plan,” “believe,” “potential,” “should” or the negative versions of those words or other comparable words. Forward-looking statements do not relate solely to historical or current facts; rather, they are based on management’s expectations as well as certain assumptions and estimates made by, and information available to, management at the time. These statements are not guarantees of future performance. These forward-looking statements are based upon Alleghany’s current expectations and are subject to a number of uncertainties and risks that could significantly affect current plans, anticipated actions and Alleghany’s future financial condition and results. Factors that could cause these forward-looking statements to differ, possibly materially, from that currently contemplated include:

7

Additional risks and uncertainties include general economic and political conditions, including the effects of a prolonged U.S. or global economic downturn or recession; changes in costs; variations in political, economic or other factors; risks relating to conducting operations in a competitive environment; effects of acquisition and disposition activities, inflation rates, or recessionary or expansive trends; changes in interest rates; extended labor disruptions, civil unrest, or other external factors over which we have no control; changes in our plans, strategies, objectives, expectations, or intentions, which may happen at any time at our discretion; and other factors discussed in Alleghany’s Report on Form 10-K for the year ended December 31, 2016 and subsequent filings with the SEC. All forward-looking statements speak only as of the date they are made and are based on information available at that time. Alleghany does not undertake any obligation to update or revise any forward-looking statements to reflect subsequent circumstances or events.

For more information, please contact:

Jack Sennott

Alleghany Corporation

212-508-8116

8

ALLEGHANY CORPORATION AND SUBSIDIARIES

Consolidated Balance Sheets

9

ALLEGHANY CORPORATION AND SUBSIDIARIES

Consolidated Statements of Earnings and Comprehensive Income

(unaudited)

10

ALLEGHANY CORPORATION AND SUBSIDIARIES

Consolidated Statements of Earnings and Comprehensive Income

(unaudited)

11