Exhibit 99.1

WILLIAM LYON HOMES REPORTS FIRST QUARTER 2015 RESULTS

NEWPORT BEACH, CA—May 8, 2015—William Lyon Homes (NYSE: WLH), a leading homebuilder in the Western U.S., announced results for its 2015 first quarter ended March 31, 2015.

2015 First Quarter Highlights (Comparison to 2014 First Quarter)

“We are very pleased to have started the year with continued positive operating momentum,” said William H. Lyon, Chief Executive Officer. “Home sales revenue increased by 35% to $189.7 million and deliveries increased by 41% to 388 units, resulting in net income of $6.7 million, or $0.18 per diluted share. While our focus last year was on expanding our geographic footprint and bolstering our supply of land within our existing markets, this year we are keenly focused on executing our financial and operational objectives and believe we are off to a good start. As the economy gains momentum and jobs continue to be created across our key Western regional markets, we are confident that we are on our way to another successful year for William Lyon Homes.”

Matthew R. Zaist, President and Chief Operating Officer stated, “We delivered another quarter of year-over-year improvement in our key operational metrics, including net new home orders, which increased by 47% to 588, and the number and dollar value of our backlog, which grew to 678 homes and $335.1 million, up 38% and 27%, respectively. Our average community count increased by 69% to 54 locations in the first quarter. We are experiencing an orderly progression of new home sales and absorption rates throughout the spring selling season, as orders have picked up momentum on a month-over-month basis throughout the quarter. This momentum has continued into the second quarter with 283 net new orders for April, a year-over-year gain of 148%. We continue to focus on new community openings and optimizing revenue in order to drive profits and returns for our shareholders.”

Operating Results

Home sales revenue for the first quarter of 2015 was $189.7 million, as compared to $140.3 million in the year-ago period, an increase of 35%. Our performance was driven by a 41% increase in the number of deliveries to 388 homes, compared to 276 homes delivered in the first quarter of 2014. Average sales price of homes delivered was $489,000 in the quarter, compared to $508,300 in the year-ago period. The modest decline in ASP primarily reflects changes in geographic and product mix contributing to closings during the quarter.

The dollar value of orders for the first quarter of 2015 was $268.2 million, an increase of 35%, from $199.2 million in the year-ago period. Net new home orders for the quarter were 588, up 47% from 400 in the first quarter of 2014. The overall increase in net new home orders was primarily driven by an increase in community count to 54 average sales locations, from 32 in the year-ago period, offset by a modest decline in absorption from 4.2 sales per month in the year-ago period to 3.6 sales per month in the current period. For the quarter, we saw monthly absorption rates range from a low of 3.0 sales per community in January to a high of 4.4 sales per community in March.

The dollar value of homes in backlog was $335.1 million as of March 31, 2015, an increase of 27% compared to $264.8 million as of March 31, 2014. The increase was driven by a 38% increase in units in backlog to 678 from 492 in the year-ago period.

Adjusted homebuilding gross margin percentage was 24.6% during the first quarter of 2015. Homebuilding gross margins for the first quarter of 2015 were 18.8%. In conjunction with the adoption of purchase accounting related to the Polygon acquisition, GAAP margins were impacted by approximately 230 basis points during the quarter.

SG&A expense during the first quarter of 2015 was 13.8% of homebuilding revenue, compared with 13.3% in the year-ago quarter. Breaking down the components of SG&A, sales and marketing expense was 6.4% of homebuilding revenue during the quarter, compared to 4.7% in the year-ago quarter, driven primarily by higher advertising costs and upfront marketing costs of approximately 0.7% of homebuilding revenue related to future community openings, as well as higher outside broker expenses of an additional 1.0% of homebuilding revenue, compared to the prior year period. General administrative expenses decreased to 7.4% of homebuilding revenue, compared to 8.7% in the year-ago quarter, as we continued to leverage off of a larger operating platform with a lower relative cost structure.

Balance Sheet Update

At quarter end, cash, cash equivalents and restricted cash totaled $30.0 million, escrow proceeds receivable totaled $7.2 million, real estate inventories totaled $1.5 billion, total debt was $995.7 million and total equity was approximately $600 million. Net debt to net book capitalization was 61.7%, and total debt to total book capitalization was 62.4% at March 31, 2015.

On March 27, 2015, the Company amended its revolving credit facility to, among other things, increase the maximum borrowing capacity from $100 million to $130 million and extend the maturity date of the facility by one year to August 7, 2017. The facility contains an accordion feature under which the Company may increase the total commitment to a maximum aggregate amount of $200 million, subject to certain conditions. The facility improves the Company’s liquidity and access to working capital.

Conference Call

The Company will host a conference call to discuss these results today, Friday, May 8, 2015 at 9:00 a.m. Pacific Time. The call will be available via both the telephone at (855) 851-4524 or (720) 634-2900, passcode #35035983, 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 May 15, 2015 by dialing (855) 859-2056 or (404) 537-3406, passcode #35035983. 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, San Diego, the San Francisco Bay Area, Phoenix, Las Vegas, Denver, Seattle and Portland. The Company has a distinguished legacy of more than 59 years of homebuilding operations, over which time it has sold in excess of 93,000 homes. The Company markets and sells its homes under the William Lyon Homes brand in all of its markets except for Colorado, where the Company operates under the Village Homes brand, and Washington and Oregon, where the Company operates under the Polygon Northwest brand.

Financial data included herein includes the Washington and Oregon operations from January 1, 2015 through March 31, 2015. There were no operations in the Company’s Washington and Oregon divisions for the three months ended March 31, 2014; therefore, period-over-period comparisons for Washington and Oregon are not meaningful (“NM”) as indicated in the comparative tables in the schedules attached to this release.

Certain statements contained in this release and the accompanying comments during our conference call that are not historical information contain forward-looking statements, including, but not limited to, statements related to: market and industry trends, the anticipated financial and operating results from execution of the Company’s growth strategy and focus on markets in the Western United States, the continued housing market recovery, expected community count growth, anticipated operating results for the second quarter of 2015 and the spring selling season, anticipated ASP, expected SG&A percentage, gross margins, future cash needs and liquidity, leverage ratios and backlog conversion rates. 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: our ability to realize the anticipated benefits from the acquisition of Polygon Northwest; our ability to integrate successfully the Polygon Northwest operation with our existing operations; worsening in general economic conditions either nationally or in regions in which we operate; conditions in our newly entered markets and newly acquired operations; worsening in markets for residential housing; decline in real estate values resulting in impairment of our real estate assets; volatility in the banking industry and credit markets; uncertainties in the capital and securities markets; terrorism or other hostilities involving the United States; building moratorium or “slow-growth” or “no-growth” initiatives that could be implemented in states in which we operate; 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; 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; changes in prices of homebuilding materials; the availability of labor and homebuilding materials; adverse weather conditions; 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; changes in governmental laws and regulations; our financial leverage and level of indebtedness and any inability to comply with financial and other covenants under our debt instruments; whether we are able to refinance the outstanding balances of our debt obligations at their maturity; anticipated tax refunds; limitations on our ability to utilize our tax attributes; limitations on our ability to reverse any remaining portion of our valuation allowance with respect to our deferred tax assets; the timing of receipt of regulatory approvals and the opening of projects; 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; 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 BALANCE SHEETS

(in thousands, except number of shares and par value per share)

WILLIAM LYON HOMES

SELECTED FINANCIAL AND OPERATING INFORMATION

(unaudited)

WILLIAM LYON HOMES

SELECTED FINANCIAL AND OPERATING INFORMATION

(unaudited)

WILLIAM LYON HOMES

SUPPLEMENTAL FINANCIAL INFORMATION

(unaudited)

Balance Sheet Data

WILLIAM LYON HOMES

SUPPLEMENTAL FINANCIAL INFORMATION

(unaudited)