Gov. Mark Dayton has repeatedly promised to sign the bill. He's scheduled to do so during a ceremony at 5 p.m. Tuesday on the front steps of Minnesota's Capitol in St. Paul.
The state Legislature gave its final stamp of approval Monday when the Senate passed the bill by a 37-30 vote. The House passed it last week.
Minnesota becomes the 12th U.S. state to legalize gay marriage, and the first in the Midwest to do it by legislative vote.