Exhibit 99.1

For Immediate Release: May 22, 2013

Jennifer Nahas

Vice President, Marketing

Griffin Capital Corporation

jnahas@griffincapital.com

Office Phone: 949-270-9332

Cell Phone: 949-433-6860

Griffin Capital Essential Asset REIT Reports First Quarter 2013

Results

Total Capitalization Exceeds Half a Billion Dollars and MFFO is more than three times the result for the

same quarter in 2012

EL SEGUNDO, Calif. (May 22, 2013) – Griffin Capital Essential Asset REIT, Inc. (the “Essential Asset REIT”) announced today its operating results for the first quarter ended March 31, 2013.

“The first quarter of 2013 picked up solidly on the strong momentum we were enjoying at the end of last year… and the momentum continues through the second quarter. We started 2013 with the acquisition of the Comcast Technical Support Headquarters outside of Denver in January, followed in February with the Boeing Capital Headquarters acquisition in Seattle, with a combined value of $39.0 million,” stated Kevin Shields, chairman and chief executive officer of the Essential Asset REIT. “The second quarter thus far has been equally robust. In April we acquired an interest in the HealthSpring Regional Headquarters in Nashville and in May we purchased the Schlumberger financial hub in Houston as well as the United Technologies Aerospace Headquarters in Charlotte.”

“Our first and second quarter acquisitions continue to expand the outstanding credit characteristics of our portfolio—including our purchase of the UTC Aerospace Headquarters property in May, over three quarters of the REIT’s net income is now generated by companies, or lease guarantors, with investment grade-rated credit quality, or have a parent company with an investment-grade rating,” added David Rupert, president of the Essential Asset REIT.

Highlights and Accomplishments in the First Quarter of 2013 and through May 3, 2013

“We could not be more pleased with the growth in our portfolio since inception, the quality of our tenant base, overall credit quality of our portfolio cash flow and the incredible support we receive from both our broker-dealer partners and new members of our lending group,” concluded Mr. Shields.

About Griffin Capital Essential Asset REIT and Griffin Capital Corporation

Griffin Capital Essential Asset REIT, Inc. is a publicly-registered non-traded REIT with a portfolio that currently includes 18 office and industrial distribution properties totaling approximately 3.8 million rentable square feet and total capitalization in excess of $500 million. The REIT’s sponsor is Griffin Capital Corporation (“Griffin Capital”), a privately-owned real estate company headquartered in Los Angeles. Led by senior executives, each with more than two decades of real estate experience collectively encompassing over $16 billion of transaction value and more than 650 transactions, Griffin Capital and its affiliates have acquired or constructed over 17 million square feet of space since 1996. Griffin Capital and its affiliates currently own and manage a portfolio consisting of over 14.8 million square feet of space, located in 28 states and representing approximately $2.5 billion in asset value. Additional information about Griffin Capital is available at www.griffincapital.com.

This press release may contain certain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Such forward-looking statements can generally be identified by our use of forward-looking terminology such as “may,” “will,” “expect,” “intend,” “anticipate,” “estimate,” “believe,” “continue,” or other similar words. Because such statements include risks, uncertainties and contingencies, actual results may differ materially from the expectations, intentions, beliefs, plans or predictions of the future expressed or implied by such forward-looking statements. These risks, uncertainties and contingencies include, but are not limited to: uncertainties relating to changes in general economic and real estate conditions; uncertainties relating to the implementation of our real estate investment strategy; uncertainties relating to financing availability and capital proceeds; uncertainties relating to the closing of property acquisitions; uncertainties relating to the public offering of our common stock; uncertainties related to the timing and availability of distributions; and other risk factors as outlined in the REIT’s prospectus, as amended from time to time. This is neither an offer nor a solicitation to purchase securities.

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GRIFFIN CAPITAL ESSENTIAL ASSET REIT, INC.

CONSOLIDATED BALANCE SHEETS

GRIFFIN CAPITAL ESSENTIAL ASSET REIT, INC.

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS

GRIFFIN CAPITAL ESSENTIAL ASSET REIT, INC.

Funds from Operations and Modified Funds from Operations

(Unaudited)

Our management believes that historical cost accounting for real estate assets in accordance with GAAP implicitly assumes that the value of real estate assets diminishes predictably over time. Since real estate values have historically risen or fallen with market conditions, many industry investors and analysts have considered the presentation of operating results for real estate companies that use historical cost accounting to be insufficient. Additionally, publicly registered, non-listed REITs typically have a significant amount of acquisition activity and are substantially more dynamic during their initial years of investment and operation. While other start-up entities may also experience significant acquisition activity during their initial years, we believe that non-listed REITs are unique in that they have a limited life with targeted exit strategies within a relatively limited time frame after the acquisition activity ceases.

In order to provide a more complete understanding of the operating performance of a REIT, the National Association of Real Estate Investment Trusts (“NAREIT”) promulgated a measure known as funds from operations (“FFO”). FFO is defined as net income or loss computed in accordance with GAAP, excluding extraordinary items, as defined by GAAP, and gains and losses from sales of depreciable operating property, adding back asset impairment write-downs, plus real estate related depreciation and amortization (excluding amortization of deferred financing costs and depreciation of non-real estate assets), and after adjustment for unconsolidated partnerships and joint ventures. Because FFO calculations exclude such items as depreciation and amortization of real estate assets and gains and losses from sales of operating real estate assets (which can vary among owners of identical assets in similar conditions based on historical cost accounting and useful-life estimates), they facilitate comparisons of operating performance between periods and between other REITs. As a result, we believe that the use of FFO, together with the required GAAP presentations, provides a more complete understanding of our performance relative to our competitors and a more informed and appropriate basis on which to make decisions involving operating, financing, and investing activities. It should be noted, however, that other REITs may not define FFO in accordance with the current NAREIT definition or may interpret the current NAREIT definition differently than we do, making comparisons less meaningful.

The Investment Program Association (“IPA”) issued Practice Guideline 2010-01 (the “IPA MFFO Guideline”) on November 2, 2010, which extended financial measures to include modified funds from operations (“MFFO”). In computing MFFO, FFO is adjusted for certain non-operating cash items such as acquisitions fees and expenses and certain non-cash items such as straight-line rent, amortization of in-place lease valuations, amortization of discounts and premiums on debt investments, nonrecurring impairments of real estate-related investments, mark-to-market adjustments included in net income (loss), and nonrecurring gains or losses included in net income (loss) from the extinguishment or sale of debt, hedges, foreign exchange, derivatives or securities holdings where trading of such holdings is not a fundamental attribute of the business plan, unrealized gains or losses resulting from consolidation from, or deconsolidation to, equity accounting, and after adjustments for consolidated and unconsolidated partnerships and joint ventures, with such adjustments calculated to reflect MFFO on the same basis. Management is responsible for managing interest rate, hedge and foreign exchange risk. To achieve our objectives, we may borrow at fixed rates or variable rates. In order to mitigate our interest rate risk on certain financial instruments, we have entered into interest rate cap agreements and in order to mitigate our risk to foreign currency exposure, if any, we may enter into foreign currency hedges. We view fair value adjustments of derivatives, impairment charges and gains and losses from dispositions of assets as non-recurring items or items which are unrealized and may not ultimately be realized, and which are not reflective of on-going operations and are therefore typically adjusted for when assessing operating performance. Additionally, we believe it is appropriate to disregard impairment charges, as this is a fair value adjustment that is largely based on market fluctuations, assessments regarding general market conditions, and the specific performance of properties owned, which can change over time. No less frequently than annually, we evaluate events and changes in circumstances that could indicate that the carrying amounts of real estate and related intangible assets may not be recoverable. When indicators of potential impairment are present, we assess whether the carrying value of the assets will be recovered through the future undiscounted operating cash flows (including net rental and lease revenues, net

proceeds on the sale of the property, and any other ancillary cash flows at a property or group level under GAAP) expected from the use of the assets and the eventual disposition. Investors should note, however, that determinations of whether impairment charges have been incurred are based partly on anticipated operating performance, because estimated undiscounted future cash flows from a property, including estimated future net rental and lease revenues, net proceeds on the sale of the property, and certain other ancillary cash flows, are taken into account in determining whether an impairment charge has been incurred. While impairment charges are excluded from the calculation of MFFO as described above, investors are cautioned that due to the fact that impairments are based on estimated future undiscounted cash flows and the relatively limited term of our operations, it could be difficult to recover any impairment charges through operational net revenues or cash flows prior to any liquidity event. We adopted the IPA MFFO Guideline, as management believes that MFFO is a beneficial indicator of our on-going portfolio performance and ability to sustain our current distribution level. More specifically, MFFO isolates the financial results of the REIT’s operations. MFFO, however, is not considered an appropriate measure of historical earnings as it excludes certain significant costs that are otherwise included in reported earnings. Further, since the measure is based on historical financial information, MFFO for the period presented may not be indicative of future results or our future ability to pay our dividends. By providing FFO and MFFO, we present information that assists investors in aligning their analysis with management’s analysis of long-term operating activities. MFFO also allows for a comparison of the performance of our portfolio with other REITs that are not currently engaging in acquisitions, as well as a comparison of our performance with that of other non-traded REITs, as MFFO, or an equivalent measure, is routinely reported by non-traded REITs, and we believe often used by analysts and investors for comparison purposes. As explained below, management’s evaluation of our operating performance excludes items considered in the calculation of MFFO based on the following economic considerations:

For all of these reasons, we believe the non-GAAP measures of FFO and MFFO, in addition to income (loss) from operations, net income (loss) and cash flows from operating activities, as defined by GAAP, are helpful supplemental performance measures and useful to investors in evaluating the performance of our real estate portfolio. However, a material limitation associated with FFO and MFFO is that they are not indicative of our cash available to fund distributions since other uses of cash, such as capital expenditures at our properties and principal payments of debt, are not deducted when calculating FFO and MFFO. Additionally, MFFO has limitations as a performance measure in an offering such as ours where the price of a share of common stock is a stated value. The use of MFFO as a measure of long-term operating performance on value is also limited if we do not continue to operate under our current business plan as noted above. MFFO is useful in assisting management and investors in assessing our on-going ability to generate cash flow from operations and continue as a going concern in future operating periods, and in particular, after the offering and acquisition stages are complete and NAV is disclosed. However, MFFO is not a useful measure in evaluating NAV because impairments are taken into account in determining NAV but not in determining MFFO. Therefore, FFO and MFFO should not be viewed as more prominent a measure of performance than income (loss) from operations, net income (loss) or to cash flows from operating activities and each should be reviewed in connection with GAAP measurements.

Neither the SEC, NAREIT, nor any other applicable regulatory body has opined on the acceptability of the adjustments contemplated to adjust FFO in order to calculate MFFO and its use as a non-GAAP performance measure. In the future, the SEC or NAREIT may decide to standardize the allowable exclusions across the REIT industry, and we may have to adjust the calculation and characterization of this non-GAAP measure.

Our calculation of FFO and MFFO is presented in the following table for the three months ended March 31, 2013 and 2012.