The action comes a day after a federal appeals court declared California’s ban on gay marriage unconstitutional, saying it was a violation of the civil rights of gay and lesbian couples.
The Washington House passed the bill on a 55-43 vote. The state Senate approved the measure last week. And Democratic Gov. Chris Gregoire is expected to sign the measure into law next week.
However, gay couples can’t begin walking down the aisle just yet.
The proposal would take effect 90 days after the governor signs, but opponents have promised to fight gay marriage with a ballot measure that would allow voters to overturn the legislative approval.
If opponents gather enough signatures to take their fight to the ballot box, the law would be put on hold pending the outcome of a November election.
Otherwise gay couples could wed starting in June.