Exhibit 99.1

INSIGHT ENTERPRISES, INC. REPORTS SECOND QUARTER 2018 RESULTS AND INCREASES FULL YEAR 2018 GUIDANCE

TEMPE, AZ – August 1, 2018 – Insight Enterprises, Inc. (NASDAQ: NSIT) (the “Company”) today reported strong financial results for the quarter ended June 30, 2018 compared to the quarter ended June 30, 2017.

In the second quarter of 2018, consolidated net sales increased 9% and consolidated gross profit increased 5% year over year. These results are primarily driven by continued strong growth in the hardware category as a result of the ongoing device refresh cycle as well as a 22% increase in services sales year over year, which includes professional services as well as cloud and maintenance offerings. Earnings from operations (“EFO”) increased 7% year over year and EFO margin was 4.1%.

The Company also announced that it has acquired Cardinal Solution Group. Inc. (“Cardinal”) effective August 1, 2018. Cardinal is a digital solutions provider based in Cincinnati, Ohio with expertise in mobile applications development, IOT and cloud enabled business intelligence. Cardinal will complement the capabilities the Company has been building within the digital innovation solution area, following the acquisitions of BlueMetal and Ignia in 2015 and 2016, respectively. The Company expects the acquisition to be neutral to earnings from operations for the balance of 2018, including projected intangible amortization.

“We are pleased with our top and bottom line financial results in the second quarter and with our team’s execution in optimizing working capital in the business, which led to Adjusted free cash flow of more than $300 million in the first half of the year,” stated Ken Lamneck, President and Chief Executive Officer. “Our strategy to grow organically while consistently driving operational efficiency across the business allows us to invest for the long term, including strategic acquisitions like Cardinal that will bring scale and reach to our already strong Digital Innovations solution area,” stated Lamneck.

KEY HIGHLIGHTS

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As services have become a larger portion of the Company’s consolidated net sales, beginning with our results of operations for the year ended December 31, 2017, the Company began reporting net sales from the provision of services and the related costs of goods sold separately from net sales of products and the related costs of goods sold. The Company continued this presentation in the three and six months ended June 30, 2018, and expects to continue this presentation in future periods. For comparability purposes, net sales and costs of goods sold for the 2017 periods have been expanded to conform to the current year presentation. These changes in presentation had no effect on previously reported total net sales, total costs of goods sold or gross profit amounts.

In conjunction with these changes in presentation, because fees earned from activities reported net are now considered services revenues, the Company reclassified certain revenue streams for which the Company acts as the agent in the transaction to net sales from services. Previously, the Company included these net revenue streams within its software and, to a lesser extent, hardware sales mix categories based on the type of product being sold (e.g., fees earned for the sale of software maintenance and certain software licenses were included in software sales and fees earned for the sale of certain third-party provided training and warranty services were included in hardware sales when the Company historically disclosed and analyzed its sales mix). For comparability purposes, the Company’s sales mix among its hardware, software and services categories for the three and six months ended June 30, 2017, as presented in the Financial Summary Table in this press release, has been reclassified to conform to the current year presentation. These reclassifications had no effect on previously reported total net sales amounts.

In discussing financial results for the three months ended June 30, 2018 and 2017 in this press release, the Company refers to certain financial measures that are not prepared in accordance with United States generally accepted accounting principles (“GAAP”). When referring to non-GAAP measures, the Company refers to such measures as “Adjusted.” See “Use of Non-GAAP Financial Measures” for additional information. A tabular reconciliation of financial measures prepared in accordance with GAAP to the non-GAAP financial measures is included at the end of this press release.

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In some instances the Company refers to changes in net sales, gross profit and earnings from operations on a consolidated basis and in North America, EMEA and APAC excluding the effects of fluctuating foreign currency exchange rates. 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 weighted average translation rate for the current period.

The tax effect of Adjusted amounts referenced herein 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.

GUIDANCE

For the full year 2018, the Company expects to deliver sales growth in the high single to low double digit range compared to 2017. The Company is also increasing its Adjusted diluted earnings per share outlook for the full year of 2018 to be between $4.50 and $4.60.

This outlook assumes:

This outlook does not reflect the repurchase of any additional shares under the Company’s currently authorized share repurchase program, assumes no current year acquisition-related expenses and excludes severance and restructuring expenses incurred during the first half of 2018 and those that may be incurred during the balance of 2018. Due to the inherent difficulty of forecasting these types of expenses, which impact net earnings and diluted earnings per share, the Company is unable to reasonably estimate the related impact of such expenses, if any, to net earnings and diluted earnings per share. Accordingly, the Company is unable to provide a reconciliation of GAAP to non-GAAP diluted earnings per share for the full year 2018 forecast.

CONFERENCE CALL AND WEBCAST

The Company will host a conference call and live web cast today at 9:00 a.m. ET to discuss second quarter 2018 results of operations. A live web cast of the conference call (in listen-only mode) will be available on the Company’s web site at http://investor.insight.com/, 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 4892118.

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USE OF NON-GAAP FINANCIAL MEASURES

The non-GAAP financial measures are referred to as “Adjusted.” Adjusted consolidated earnings from operations, Adjusted consolidated net earnings and Adjusted diluted earnings per share exclude (i) severance and restructuring expenses, (ii) certain acquisition-related expenses, and (iii) the tax effects of each of these items, as applicable. The Company excludes these items 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. Adjusted free cash flow is the Company’s net cash provided or used by operating activities adjusted for (i) purchases of property and equipment and (ii) the net borrowings or repayments on the inventory financing facility. Adjusted return on invested capital (“ROIC”) excludes (i) severance and restructuring expenses, (ii) certain acquisition-related expenses, and (iii) a loss on sale of the Company’s Russia business in the 2017 period.

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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FINANCIAL SUMMARY TABLE (CONTINUED)

(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 2018 financial results, sales growth and Adjusted diluted earnings per share for the full year 2018, and the assumptions relating thereto, as well as the Company’s anticipated effective tax rate, capital expenditures and plans concerning repurchases under the Company’s currently authorized share repurchase program, the Company’s expectations for earnings from operations and amortization of intangibles from the Cardinal acquisition, the Company’s expectations regarding cash flow, and the Company’s expectations for the future presentation of services net sales, 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, 2017 and in other of the Company’s subsequent filings with the Securities and Exchange Commission:

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, except as may be required by law, does not intend to update, any forward-looking statements. The Company does not endorse any projections regarding future performance that may be 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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INSIGHT ENTERPRISES, INC. AND SUBSIDIARIES

RECONCILIATION OF GAAP TO NON-GAAP FINANCIAL MEASURES (CONTINUED)

(IN THOUSANDS, EXCEPT PER SHARE DATA)

(UNAUDITED)

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