Gam, who was director Sidney Lumet's first wife and a bridesmaid at Grace Kelly's 1956 wedding to Prince Rainier, died of respiratory failure at Cedars-Sinai Medical Center in Los Angeles on March 22, publicist Nancy Willen said.
The veteran actress also appeared opposite Gregory Peck in "Night People" (1954) and "Shoot Out" (1971), in William Dieterle's "Magic Fire" (1955), with Victor Mature in "Hannibal" (1959) and with Jane Fonda in Alan J Pakula's "Klute" (1971).
Born in Pittsburgh on April 2, 1927, Gam was raised in New York City. A founding member of The Actors Studio, she landed a role on Broadway in 1946 in "A Flag Is Born", written by Ben Hecht, then made her movie debut in The Thief (1952) opposite Ray Milland.
Gam was a leading member of the Minnesota Theater Company during the opening season (1963) of the Guthrie Theater in Minneapolis with Zoe Caldwell, Hume Cronyn and Jessica Tandy.