Bellevue-based T-Mobile USA will support Washington's Referendum 74, the company announced Monday.
The referendum, which would affirm the legislatively backed law that legalizes marriage for same-sex couples, will be on the ballot in November.
The company will contribute $25,000 to Washington United for Marriage, the group campaigning to pass the referendum, according to company officials.
Other local companies and executives also have announced support for the law and have donated to Washington United for Marriage, including Microsoft CEO Steve Ballmer and Microsoft co-founder Bill Gates. Microsoft also affirmed its support of the marriage law in January, before it was approved by the legislature.