The 55-year-old "Frasier" and "Cheers" star's divorce from Camille, his wife of 13 years, was finalized two weeks ago.
Walsh, 29, is a British former flight attendant.
People.com said a reception at the Plaza Hotel followed the wedding ceremony at the theater where Grammer recently starred in the revival of the musical "La Cage aux Folles."
Among the wedding guests were actors David Hyde Pierce and Alan Arkin, the report said.
"Kelsey Grammer and Kayte Walsh were married today at a private ceremony for family and friends," his representative confirmed in a statement issued to People.com.