Exhibit 99.1

INSIGHT ENTERPRISES, INC. REPORTS SECOND QUARTER 2013 RESULTS

TEMPE, AZ – August 8, 2013 – Insight Enterprises, Inc. (NASDAQ: NSIT) (the “Company”) today reported results of operations for the quarter ended June 30, 2013.

For the second quarter of 2013:

“During the second quarter, we continued to see soft top line performance, but we drove gross margin expansion through higher services sales and a strategic focus on more profitable product sales. We also maintained strict discipline around the costs in our business,” stated Ken Lamneck, President and Chief Executive Officer, “We are continuing to focus on growing our solutions-selling expertise around key technologies and in select markets and verticals and believe that this will bring value to our clients and shareholders over time,” added Lamneck.

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SEGMENT OVERVIEW

In North America, net sales were $923.1 million for the second quarter of 2013, down 7% compared to net sales of $993.0 million for the second quarter of 2012. Net sales of hardware and software decreased 10% and 4%, respectively, year to year, while net sales of services remained flat year over year. Gross profit of $124.7 million was down 4% year to year, with gross margin increasing to 13.5% from 13.1% in the second quarter of 2012. Selling and administrative expenses in North America in the second quarter of 2013 remained flat year over year. The year over year comparison was affected by a prior year gain of $1.2 million on the sale of a portfolio of non-core service contracts as a reduction of selling and administrative expenses in the second quarter of 2012. During the second quarter of 2013, North America recorded severance and restructuring expenses, net of adjustments, of $967,000, $638,000 net of tax, compared to $894,000, $552,000 net of tax, during the second quarter of 2012. As a result, earnings from operations in North America decreased 15% year to year to $33.4 million, or 3.6% of net sales, in the second quarter of 2013, compared to $39.1 million, or 3.9% of net sales, in the second quarter of 2012.

The Company’s EMEA operating segment reported net sales of $421.1 million for the second quarter of 2013, a decrease of 8% in U.S. dollars compared to the second quarter of 2012. Excluding the effects of foreign currency movements, net sales decreased 9% year to year. Net sales of services were up 42% year over year, while net sales of hardware and software declined 21% and 4%, respectively, year to year, all in U.S. dollars. Excluding the effects of foreign currency movements, net sales of services increased 41%, while net sales of hardware and software declined 19% and 6%, respectively, compared to the second quarter of 2012. Gross profit of $54.2 million was also down 8% year to year in U.S. dollars, 9% excluding the effects of foreign currency movements, with gross margin remaining flat at 12.9% in both periods. Selling and administrative expenses in EMEA in the second quarter of 2013 decreased 1%, or $623,000, compared to the second quarter of 2012 in U.S. dollars and, excluding the effects of foreign currency movements, were also down 1% compared to the prior year period. During the second quarter of 2013, EMEA recorded severance and restructuring expenses, net of adjustments, of $2.2 million, $1.9 million net of tax, compared to $1.5 million, $1.0 million net of tax, during the second quarter of 2012. As a result, earnings from operations in EMEA decreased 47% year to year to $5.7 million, or 1.4% of net sales, in the second quarter of 2013 compared to $10.8 million, or 2.4% of net sales, in the second quarter of 2012.

The Company’s APAC operating segment reported net sales of $72.4 million for the second quarter of 2013, a decrease of 5% compared to the second quarter of 2012 in U.S. dollars, a decrease of 2% excluding the effects of foreign currency movements. Gross profit was $12.0 million, an increase of 3% year over year in U.S. dollars, 5% excluding the effects of foreign currency movements, with gross margin increasing to 16.6% for the second quarter of 2013 from 15.3% in the second quarter of 2012. Selling and administrative expenses in APAC increased 4%, or $227,000, compared to the second quarter of 2012 in U.S. dollars. Excluding the effects of foreign currency movements, selling and administrative expenses increased 5% compared to the second quarter of last year. As a result, earnings from operations in APAC increased 2% year over year to $5.5 million, or 7.6% of net sales, in the second quarter of 2013 compared to $5.4 million, or 7.0% of net sales, in the second quarter of 2012.

Throughout this “Segment Overview” section, the Company refers to changes in net sales, gross profit and selling and administrative expenses in EMEA and APAC excluding the effects of foreign currency movements. In computing these changes and percentages, the Company compares the current year amount as translated into U.S. dollars under the applicable accounting standards to the prior year amount in local currency translated into U.S. dollars utilizing the average translation rate for the current period.

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Net of tax amounts referenced above were computed using the statutory tax rate for the taxing jurisdictions in the operating segment in which the related expenses were recorded, adjusted for the effects of valuation allowances on net operating losses in certain jurisdictions.

UPDATED GUIDANCE

The Company currently expects diluted earnings per share for the full year of 2013 to be between $1.70 and $1.85.

This outlook includes the following assumptions:

This outlook excludes severance and restructuring expenses incurred during 2013.

CONFERENCE CALL AND WEBCAST

The Company will host a conference call and live web cast today at 5:00 p.m. ET to discuss second quarter 2013 results of operations. A live web cast of the conference call (in listen-only mode) will be accessible online through the investor relations section of the Company’s web site, www.insight.com, at http://nsit.client.shareholder.com/events.cfm, and a replay of the web cast will be available on the Company’s web site for a limited time following the call. To listen to the live web cast by telephone, call 1-877-402-8904 if located in the U.S., 678-809-1029 for international callers, and enter the access code 20607805.

USE OF NON-GAAP FINANCIAL MEASURES

The non-GAAP financial measures exclude severance and restructuring expenses in 2013 and 2012, a gain on bargain purchase in 2012 and the tax effect of these items. The Company excludes these charges when internally evaluating earnings from operations, tax expense, net earnings and diluted earnings per share for the Company and earnings from operations for each of the Company’s operating segments. These non-GAAP measures are used to evaluate financial performance against budgeted amounts, to calculate incentive compensation, to assist in forecasting future performance and to compare the Company’s results to those of the Company’s competitors. The Company believes that these non-GAAP financial measures are useful to investors because they allow for greater transparency, facilitate comparisons to prior periods and the Company’s competitors’ results and assist in forecasting performance for future periods. These non-GAAP financial measures are not prepared in accordance with GAAP and may be different from non-GAAP financial measures presented by other companies. Non-GAAP financial measures should not be considered as a substitute for, or superior to, measures of financial performance prepared in accordance with GAAP.

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FINANCIAL SUMMARY TABLE

(DOLLARS IN THOUSANDS, EXCEPT PER SHARE DATA)

(UNAUDITED)

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FORWARD-LOOKING INFORMATION

Certain statements in this release and the related conference call and web cast are “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements, including the Company’s expected 2013 net sales, financial results, earnings performance and diluted earnings per share, and the assumptions relating thereto, including the gross profit effect of partner program changes and the effective tax rate, are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified. Future events and actual results could differ materially from those set forth in, contemplated by, or underlying the forward-looking statements. There can be no assurances that the results discussed by the forward-looking statements will be achieved, and actual results may differ materially from those set forth in the forward-looking statements. Some of the important factors that could cause the Company’s actual results to differ materially from those projected in any forward-looking statements, include, but are not limited to, the following, which are discussed in “Risk Factors” in Part I, Item 1A of the Company’s Annual Report on Form 10-K for the year ended December 31, 2012:

Additionally, there may be other risks that are otherwise described from time to time in the reports that the Company files with the Securities and Exchange Commission. Any forward-looking statements in this release should be considered in light of various important factors, including the risks and uncertainties listed above, as well as others. The Company assumes no obligation to update, and does not intend to update, any forward-looking statements. The Company does not endorse any projections regarding future performance made by third parties.

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INSIGHT ENTERPRISES, INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF OPERATIONS

(IN THOUSANDS, EXCEPT PER SHARE DATA)

(UNAUDITED)

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INSIGHT ENTERPRISES, INC. AND SUBSIDIARIES

CONSOLIDATED BALANCE SHEETS

(IN THOUSANDS)

(UNAUDITED)

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INSIGHT ENTERPRISES, INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF CASH FLOWS

(IN THOUSANDS)

(UNAUDITED)

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INSIGHT ENTERPRISES, INC. AND SUBSIDIARIES

RECONCILIATION OF GAAP TO NON-GAAP FINANCIAL MEASURES

(IN THOUSANDS, EXCEPT PER SHARE DATA)

(UNAUDITED)

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