Theatre couple revealed their engagement to People magazine during the Whitney Gala on Oct. 19.
Gummer, the daughter of Oscar-winning actress Meryl Streep and sculptor Donald Gummer, met Walker while the two were appearing in the Broadway revival of Les Liaisons Dangereuses in 2008. "He was the Keanu to my Uma," Gummer told People. "We were kind of pals first. It was a drawn-out thing."
Walker, who also appeared in the 2007 production of Inherit the Wind and Bloody Bloody Andrew Jackson at the Public Theater, proposed on Oct. 18.
The actress was sporting an antique-set engagement ring and said her family is "all very happy … we're very, very smiley."