Exhibit 99.1

FOR IMMEDIATE RELEASE

MOBILE MINI REPORTS 2012 FIRST QUARTER RESULTS

Fifth Sequential Comparable Quarter Increase in Lease Revenues

Enters Two New Markets

Tempe, AZ – May 4, 2012 — Mobile Mini, Inc. (NASDAQ GS: MINI) today reported GAAP and non-GAAP financial results for the first quarter ended March 31, 2012.

First Quarter 2012 Compared to First Quarter 2011

Other First Quarter 2012 Highlights

Non-GAAP reconciliation tables are on page 5 of this press release, and show the nearest comparable GAAP results to the non-GAAP results.

Business Overview

Mobile Mini’s Chairman, President & CEO, Steven Bunger stated, “Although our first quarter is historically our seasonally slowest, we experienced comparable quarter gains in our most important performance benchmarks – utilization, yield and, as a result, lease revenues. This was in fact the fifth sequential reporting period of comparable quarter lease revenue growth. That said, we were less than satisfied by the rate of lease revenue growth in North America. Our core business activity was not as robust as we would have expected even in our seasonally weakest quarter. In addition, the lower growth can be attributed to a higher volume in the number of pick-ups in the first quarter given our unusually high holiday rental demand the prior year and changes we made to our call center. During the first quarter, our National Sales Center team was structured into dedicated in-bound and out-bound groups. This focus will allow us to more effectively size our call center teams to put more emphasis on customer relationships, account ownership and finding new opportunities. With our sales staff refocused on getting storage units on rent with our core longer term customers, utilization has improved from a first quarter average of 56.8% to 57.3% at the end of March, up to 57.6% at April 30^th. We believe this improvement in utilization will continue and translate into increased lease revenues and profitability as the year progresses.”

Mr. Bunger continued, “Non-GAAP EBITDA and non-GAAP EBITDA margin also fell below our expectations due to several large expense items designed to support growth over the longer term. The three most significant items included approximately $700,000 associated with the start-up of our consumer initiative, such as leasing warehouse space, hiring and training personnel, and advertising production costs. We also incurred approximately $500,000 of expenses from lease fleet repositioning and new location start-up costs. Finally, there was a 13% increase in deliveries of steel and mobile offices, which drove higher repair and maintenance expenses.”

Mr. Bunger further noted, “The upward trend in yield continued into 2012 with a 4.4% comparable quarter improvement for the first quarter, which relates to increased trucking revenues, product mix owing to the increase in office rentals, plus a continuation of rental rate increases.”

Discussing yards and branches opened in 2011, Mr. Bunger pointed out, “Thus far we are very encouraged by their performance. By ramping up units on lease, many of the new locations are already EBITDA positive and others are close to achieving that goal. Thus far this year, we have entered two new markets, Rochester, NY as we announced in February and more recently, Palm Springs, CA, both with low-cost greenfield operational yards. At the end of March, we acquired the lease assets of the second largest mobile storage company in Calgary, AB, which has been integrated into our existing Calgary operations. We are still on track to enter a minimum of eight new markets this year, with the next yard scheduled to open in Lexington, KY during the second quarter. We also consolidated our operations in Scotland, and now serve customers in and around Edinburgh through our Glasgow branch. With regard to our U.K. operations, in the aggregate they are doing an excellent job of growing lease revenues, which were up 12.5% from the first quarter of 2011.”

Moving on to Mobile Mini’s new and expanded consumer initiative, Mr. Bunger went on to say, “We should be up and running in Phoenix, San Diego, Denver, Austin, Atlanta, Jacksonville and Minneapolis, by the end of the second quarter. Mobile Mini will deliver empty containers to homeowners and when loaded, we will pick them up and deliver them to our indoor warehouse. To support and grow this enterprise, we are using idle fleet that has been customized with consumer-oriented features and exterior branding, rollout out a new website, plus we have mass advertising planned.”

Mark Funk, Mobile Mini’s Executive Vice President & CFO, noted, “Inclusive of the 2012 first quarter, we have generated free cash flow for 17 consecutive quarters. First quarter free cash flow of $13.9 million made possible the pay down of $4.2 million of debt, after payment of $7.4 million of financing costs for our new ABL and $5.0 million of capital expenditures. As we announced in February, our new ABL reduces our interest rate on borrowings by 50 basis points while increasing the maximum principal amount to $900.0 million from $850.0 million, and extending the new ABL maturity to February 22, 2017.”

He continued, “Since the acquisition of Mobile Storage Group in mid-2008, we have generated free cash flow of $272.4 million and paid down $239.5 million of debt. As a result of our reduced borrowings and better rates under our new ABL, our 2012 first quarter interest expense was reduced by 16.4%, or over $2 million, compared to the first quarter of 2011.”

Mr. Bunger concluded, “We don’t believe the comparable quarter growth rates of the first quarter are indicative of the year as a whole. As the year unfolds, we expect to achieve meaningful gains in comparable quarter non-GAAP EBITDA, spurred by more substantial increases in lease revenues. Our core business, geographic expansion plans and new consumer initiatives have a strong financial infrastructure in which to prosper.”

EBITDA, EBITDA margin, non-GAAP SG&A and free cash flow are non-GAAP financial measures as defined by Securities and Exchange Commission (“SEC”) rules. Reconciliations of EBITDA, EBITDA margin, and free cash flow to the most directly comparable GAAP financial measures can be found later in this release.

Conference Call

Mobile Mini will host a conference call today, Friday, May 4, 2012 at 12 noon ET to review these results. To listen to the call live, dial (201) 493-6739 and ask for the Mobile Mini Conference Call or go to www.mobilemini.com and click on the Investors section. Additionally, a slide presentation that will accompany the call will be posted at www.mobilemini.com on the Investors section and will be available in advance and after the call. We will also post the reconciliation of non-GAAP financial measures used in the slide show to the most directly comparable GAAP financial measures. Please go to the website 15 minutes early to download and install any necessary audio software. If you are unable to listen live, a replay of the conference call can be accessed for approximately 14 days after the call at Mobile Mini’s website.

Mobile Mini, Inc. is the world’s leading provider of portable storage solutions through its total lease fleet of over 236,600 portable storage containers and office units with 134 locations in the U.S., United Kingdom, Canada and The Netherlands. Mobile Mini is included on the Russell 2000^® and 3000^® Indexes and the S&P Small Cap Index.

This news release contains forward-looking statements, particularly regarding growth, free cash flow, ability to enter new markets, increase in utilization, the ability to strengthen, grow and expand our operations, increasing debt pay down, and new consumer initiatives, which involve risks and uncertainties that could cause actual results to differ materially from those currently anticipated. Risks and uncertainties that may affect future results include those that are described from time to time in the Company’s SEC filings. These forward-looking statements represent the judgment of the Company, as of the date of this release, and Mobile Mini disclaims any intent or obligation to update forward-looking statements.

(See Accompanying Tables)

Mobile Mini, Inc.

Condensed Consolidated Statements of Income

(Unaudited)

(in thousands except per share data)/(includes effects of rounding)

This press release includes the financial measures “EBITDA”, “EBITDA margin”, “non-GAAP SG&A” and “free cash flow”. These measurements are deemed “non-GAAP financial measures” under rules of the SEC, including Regulation G. This non-GAAP financial information may be determined or calculated differently by other companies.

EBITDA is defined as net income before interest expense, income taxes, depreciation and amortization, and if applicable, debt restructuring or extinguishment costs. We typically further adjust EBITDA to ignore the effect of what we consider transactions or events not related to our core business to arrive at non-GAAP EBITDA in the reconciliation below. The GAAP financial measure that is most directly comparable to EBITDA is net cash provided by operating activities. EBITDA margin is calculated by dividing consolidated EBITDA by total revenues. The GAAP financial measure that is most directly comparable to EBITDA margin is operating margin, which represents operating income divided by revenues. We present EBITDA and EBITDA margin because we believe they provide useful information regarding our ability to meet our future debt payment requirements, capital expenditures and working capital requirements and they provide an overall evaluation of our financial condition. In addition, EBITDA is a component of certain financial covenants under our revolving credit facility and is used to determine our available borrowing ability and the interest rate. We include EBITDA in the earnings announcement to provide transparency to investors. EBITDA has certain limitations as an analytical tool and should not be used as a substitute for net income, cash flows, or other consolidated income or cash flow data prepared in accordance with GAAP or as a measure of our profitability or our liquidity. EBITDA margin is presented along with the operating margin so as not to imply that more emphasis should be placed on it than the corresponding GAAP measure.

Free cash flow is defined as net cash provided by operating activities, less net cash used in investing activities, excluding acquisitions. Free cash flow is a non-GAAP financial measure and is not intended to replace net cash provided by operating activities, the most directly comparable GAAP financial measure. We present free cash flow because we believe it provides useful information regarding our liquidity and ability to meet our short-term obligations. In particular, free cash flow indicates the amount of cash available after capital expenditures for, among other things, investments in the Company’s existing businesses, debt service obligations and strategic acquisitions.

Non-GAAP SG&A permits a comparative assessment of our SG&A expenses by excluding certain one-time expenses to make a more meaningful comparison of our operating performance.

A reconciliation of EBITDA to net cash provided by operating activities and net income to EBITDA and non-GAAP EBITDA, as well as a reconciliation of net cash provided by operating activities to free cash flow, follows. These reconciliations are in thousands and include effects of rounding.

Mobile Mini, Inc.

Condensed Consolidated Balance Sheets

(in thousands except par value data)

(includes effects of rounding)