The couple wed in a civil union ceremony in Collingswood, NJ on Wednesday, reports the New York Times.
The Top Gun actress met Leis in 2000 after hiring her at a Florida restaurant she owned with her second husband Fred Tillman.
McGillis - who first came out as a lesbian in an interview with SheWired.com in 2009 - recalled the occasion with happiness.
“That was one of those moments when somebody asked me a question, my kids had gone from home, so I really didn’t have to protect anyone by skirting the question, and I just decided to be absolutely honest," she said.
McGillis has two daughters, 20-year-old Kelsey and 17-year-old Sonora, from her marriage to Tillman.