Gam's career began on Broadway and in television, after which she moved on to films, appearing first in the 1952 film noir The Thief with Ray Milland.

Another notable role was Herodias in the 1961 film King of Kings.

She shared the Silver Bear for Best Actress award with Viveca Lindfors at the 1962 Berlin Film Festival, for their performances in Tad Danielewski's No exit.

She appeared in a few more American films before finding work in Europe. Gam returned to the U.S. to appear in small parts in films including Klute in 1971 before taking up documentary film making.

In 2003 she appeared in the rotating cast of the Off-Broadway staged reading of Wit & Wisdom.

In 2004, she appeared in one of a series of ads for the Royal Bank of Scotland. Filmed at Saint Bartholomew's Episcopal Church, New York, the ad included Gam in the role of a concerned mother who is at first distressed when a wedding seems about to go haywire due to a vacillating, overly talkative groom.

Gam's first husband was director Sidney Lumet.

She was a bridesmaid at the wedding of her close friend Grace Kelly to Prince Rainier in Monaco.

Rita is of French and Romanian descent.