Exhibit 99.1

WILLIAM LYON HOMES REPORTS THIRD QUARTER 2017 RESULTS

110% INCREASE IN NET INCOME AVAILABLE TO COMMON STOCKHOLDERS; 77% INCREASE IN PRE-TAX INCOME; 260 BASIS POINT IMPROVEMENT IN OPERATING MARGIN

NEWPORT BEACH, CA— October 31, 2017 — William Lyon Homes (NYSE: WLH), a leading homebuilder in the Western U.S., announced results for its third quarter ended September 30, 2017.

2017 Third Quarter Highlights (Comparison to 2016 Third Quarter)

“We are extremely pleased with our results for the third quarter, with significant improvements in homebuilding revenues to $490.3 million, up 43%, pre-tax income of $44.0 million, up 77%, net income of $27.4 million, up 110%, and earnings per share on a diluted basis of $0.71, up 109%,” said Matthew R. Zaist, President and Chief Executive Officer. “As we expected, the third quarter represented an inflection point for our GAAP homebuilding gross margins, which were 18.1%, an increase of 160 basis points above the second quarter of 2017 and 150 basis points year-over-year. Our third quarter results included operating margin improvement of 260 basis points year-over-year, which is a testament to improving our operating discipline around land acquisition and cost control, as well as the strength of our Western markets.”

Mr. Zaist continued, “Our third quarter net new home orders were up 19% year-over-year, to 774, and our monthly absorption rate for the third quarter was 3.0 sales per community, up from 2.8 sales per community in the third quarter of 2016. The strong performance year-to-date, as well as our strong backlog, positions us well to achieve our goals for the full year. The Company expects fourth quarter results to include backlog conversion of 85% to 92%, sequential gross margin improvement of 50 to 70 basis points, sequential SG&A improvement of 20 to 30 basis points and pre-tax income of $60.0 million to $65.0 million.”

Operating Results

Home sales revenue for the third quarter of 2017 was $490.3 million, as compared to $342.6 million in the year-ago period, an increase of 43%. The increase was driven by a 26% increase in deliveries to 851 homes, compared to 673 in the third quarter of 2016, combined with an increase in the average sales price of homes delivered to $576,200, up 13% from the prior year.

The dollar value of orders for the third quarter of 2017 was $425.5 million, an increase of 22%, from $348.7 million in the year-ago period. Net new home orders for the quarter were 774, up 19% from 651 in the third quarter of 2016. The overall increase in net new home orders was driven by an increase in community count to 86 average sales locations, from 78 in the year-ago period, combined with a 7% increase in the monthly absorption rate from 2.8 sales per community in the year-ago period to 3.0 sales per community in the current period.

The dollar value of homes in backlog was $699.3 million as of September 30, 2017, an increase of 18%, compared to $591.0 million as of September 30, 2016. The increase was driven by a 13% increase in units in backlog to 1,208 from 1,071 in the year-ago period and a 5% increase in ASP in backlog to $578,900 from $551,900 in the third quarter of 2016.

Homebuilding gross margin percentage for homes closed during the third quarter of 2017 was 18.1%, up from 16.6% gross margin percentage in the year-ago period and 16.5% in the second quarter of 2017. Adjusted homebuilding gross margin percentage for the quarter was 23.6%, up from 22.2% adjusted gross margin percentage in the prior year period and 22.1% in the second quarter of 2017.

Sales and marketing expense during the third quarter of 2017 was 4.5% of homebuilding revenue, compared to 5.3% in the second quarter of 2016, driven by lower advertising costs, compared to the year-ago quarter of 5.3% of revenue. The Company has focused on more efficient advertising spending using social media and mobile applications to offset higher outside broker costs. General and administrative expenses decreased to 4.7% of homebuilding revenue, compared to 5.1% in the year-ago quarter, as we continue to benefit from a lower relative cost structure due to the higher revenue and positive operating leverage.

Balance Sheet Update

At quarter end, cash and cash equivalents totaled $43.6 million, real estate inventories totaled $1.9 billion, total assets were $2.1 billion and total equity was $826.0 million. Total debt to book capitalization was 57.1%, and net debt to total capital (net of cash) was 56.1% at September 30, 2017, compared to 61.6% and 60.8% at September 30, 2016, and 58.6% and 57.6% at December 31, 2016, respectively.

Conference Call

The Company will host a conference call to discuss these results today, Tuesday, October 31, 2017 at 9:00 a.m. Pacific Time. The call will be available via both the telephone at (855) 851-4524 or (720) 634-2900, conference ID #99544612, or through the Company’s website at www.lyonhomes.com in the Investor Relations section of the site.

A replay of the call will be available through November 7, 2017 by dialing (855) 859-2056 or (404) 537-3406, conference ID #99544612. A webcast replay of the call will also be available on the Company’s website approximately two hours after the broadcast.

About William Lyon Homes

William Lyon Homes is one of the largest Western U.S. regional homebuilders. Headquartered in Newport Beach, California, the Company is primarily engaged in the design, construction, marketing and sale of single-family detached and attached homes in California, Arizona, Nevada, Colorado, Washington and Oregon. Its core markets include Orange County, Los Angeles, the Inland Empire, the San Francisco Bay Area, Phoenix, Las Vegas, Denver, Portland and Seattle. The Company has a distinguished legacy of more than 60 years of homebuilding operations, over which time it has sold in excess of 101,000 homes. The Company markets and sells its homes under the William Lyon Homes brand in all of its markets except for Washington and Oregon, where the Company operates under the Polygon Northwest brand.

Forward-Looking Statements

Certain statements contained in this release and the accompanying comments during our conference call that are not historical information may constitute “forward-looking statements” as defined by the Private Securities Litigation Reform Act of 1995, including, but not limited to, forward-looking statements related to: anticipated pre-tax income, gross margin performance, backlog conversion rates, operating and financial results for the fourth quarter of 2017 and full year 2017, community count growth and project performance, market and industry trends, the continued housing market recovery, average sale price of homes to be closed in various periods, SG&A percentage, future cash needs and liquidity, minority interest from our homebuilding joint ventures, leverage ratios and reduction strategies and land acquisition spending. The forward-looking statements involve risks and uncertainties and actual results may differ materially from those projected or implied. The Company makes no commitment, and disclaims any duty, to update or revise any forward-looking statements to reflect future events or changes in these expectations. Further, certain forward-looking statements are based on assumptions of future events which may not prove to be accurate. Factors that may impact such forward-looking statements include, among others: adverse weather conditions and impact from natural disasters such as the recent fire activity in Northern California; the availability of labor and homebuilding materials and increased construction cycle times; the availability and timing of mortgage financing; our financial leverage and level of indebtedness and any inability to comply with financial and other covenants under our debt instruments; continued volatility and worsening in general economic conditions either internationally, nationally or in regions in which we operate; increased outside broker costs; increased costs of homebuilding materials; changes in governmental laws and regulations and compliance, increased costs, fees and delays associated therewith; potential changes to the tax code; worsening in markets for residential housing; the impact of construction defect, product liability and home warranty claims, including the adequacy of self-insurance accruals, and the applicability and sufficiency of our insurance coverage; defects in manufactured products or other homebuilding materials; decline in real estate values resulting in impairment of our real estate assets; volatility in the banking industry, credit and capital markets; terrorism or other hostilities involving the United States and other geopolitical risks; building moratorium or “slow-growth” or “no-growth” initiatives that could be implemented in states in which we operate; changes in mortgage and other interest rates; conditions in the capital, credit and financial markets, including mortgage lending standards and the availability of mortgage financing; changes in generally accepted accounting principles or interpretations of those principles; competition for home sales from other sellers of new and resale homes;

cancellations and our ability to realize our backlog; the occurrence of events such as landslides, soil subsidence and earthquakes that are uninsurable, not economically insurable or not subject to effective indemnification agreements; limitations on our ability to utilize our tax attributes; whether an ownership change occurred that could, under certain circumstances, have resulted in the limitation of our ability to offset prior years’ taxable income with net operating losses; the timing of receipt of regulatory approvals and the opening of projects; the availability and cost of land for future development; and additional factors discussed under the sections captioned “Risk Factors” included in our annual and quarterly reports filed with the Securities and Exchange Commission. The foregoing list is not exhaustive. New risk factors may emerge from time to time and it is not possible for management to predict all such risk factors or to assess the impact of such risk factors on our business.

Investor/Media Contacts:

Larry Clark

Financial Profiles, Inc.

(310) 622-8223

WLH@finprofiles.com

WILLIAM LYON HOMES

CONSOLIDATED STATEMENTS OF OPERATIONS

(in thousands except number of shares and per share data)

(unaudited)

WILLIAM LYON HOMES

CONSOLIDATED STATEMENTS OF OPERATIONS

(in thousands except number of shares and per share data)

(unaudited)

WILLIAM LYON HOMES

CONSOLIDATED BALANCE SHEETS

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WILLIAM LYON HOMES

SELECTED FINANCIAL AND OPERATING INFORMATION

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WILLIAM LYON HOMES

SELECTED FINANCIAL AND OPERATING INFORMATION

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WILLIAM LYON HOMES

SELECTED FINANCIAL AND OPERATING INFORMATION

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WILLIAM LYON HOMES

SUPPLEMENTAL FINANCIAL INFORMATION

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WILLIAM LYON HOMES

SUPPLEMENTAL FINANCIAL INFORMATION

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WILLIAM LYON HOMES

SUPPLEMENTAL FINANCIAL INFORMATION

(dollars in thousands)

(unaudited)