During her radio performances, she met Karl Swenson, who portrayed the Scandinavian Lars Hanson on Michael Landon's Little House on the Prairie NBC television series. Tompkins herself guest starred twice on Little House. The couple married sometime after Swenson divorced his first wife, the former Virginia Hanscom (1908–2003). They were living in southern California by 1957.

In the 1930s, Tompkins was married to actor Steve Appleby. In the 1940s, she was married to actor Bruce MacFarlane.

In 1938, at the age of 23, Tompkins joined Henry Fonda in performing plays in White Plains, New York. She appeared on Broadway in New York City in stage productions of Fly Away Home (1935), (her first Broadway appearance) Pride and Prejudice (1935), The Golden Journey (1936) and My Sister Eileen (1940).

Tompkins first appeared on television in 1954 at the age of thirty-nine in the segment “Guest in the House” of NBC's Kraft Television Theater. Four years later, she appeared as Sarah Sheldon in the 1958 episode “The Spy” of the Goodyear Theatre. That same year, she portrayed a woman named “Patience” in NBC's western series The Californians, and as a gossip columnist named Beverly King in an episode of The Danny Thomas Show. Subsequent appearances were on the situation comedies, The Donna Reed Show, and Bachelor Father. In 1960, she played Martha in “The Twisted Root” of the syndicated series, The Brothers Brannagan.

Tompkins performed on radio in the soap opera role of Nora Drake on This Is Nora Drake, which ran on CBS radio until 1959. Her other roles on radio programs included those shown in the table below.

In 1960, she also appeared in three Warner Brothers/ABC series, Maverick, as Mary Burch in the episode “Bullet for the Teacher”; Hawaiian Eye, as a tourist in “Man in a Rage”, and The Roaring Twenties, as Celia Morton in “Layoff Charley”. In 1960-1961, she appeared twice on Boris Karloff's Thriller, starring Boris Karloff. Between 1962-1964, she made three guest appearances on Perry Mason, including the role of murderer Florence Holman in the 1962 episode, "The Case of the Poison Pen Pal," and Emily Green in "The Case of the Deadly Verdict" in 1963. As Sadie Norman in the 1964 episode "The Case of the Sleepy Slayer", she appeared with husband Karl Swenson, who played her husband Charles Norman.

Tompkins appeared twice with David Janssen on the ABC television series The Fugitive. In the 1967 episode Dr. Richard Kimble, using the alias "Douglas Beckett", is hired as a chauffeur for a wealthy family, with Tompkins playing the mother, Madge Glenn. Her daughter Joanne Glenn, portrayed by Katherine Crawford, is involved with the pool maintenance man, Dan Holt, played by Mark Goddard, formerly of Lost in Space and Many Happy Returns. Madge tries to break up her daughter's romance, and then Holt discovers the identity of Dr. Kimble and blackmails him to provide cover so that Holt can continue to see Joanne without the family finding out about the ongoing relationship. Pete Duel, prior to Alias Smith and Jones, played a young socialite in the 1967 episode. She also appeared in the 1967 episode "There goes the Ballgame" as Rose. She is also fondly remembered by fans of classic television as the mother to Don Grady's TV wife Tina Cole on My Three Sons playing the recurring role of Lorraine Miller. She played the part nine times during the period from 1967-70.

In the 1962-1963 television season, Tompkins played legal secretary Trudy Wagner in Edmond O'Brien's NBC legal drama Sam Benedict, co-starring Richard Rust. From 1967-1970, she guest starred nine times as Lorraine Miller in Fred MacMurray's CBS situation comedy, My Three Sons, with her last appearance in the episode "St. Louis Blues" on December 19, 1970.

Tompkins's last roles were in 1980, as Grandma Gertie Wells in the episode “Generations” of ABC’s Eight Is Enough and as a woman physician in The Night the City Screamed, another television film.

After World War II, Tompkins became a foster parent for a war orphan, a handicapped Polish youth named Tomek Machcinski, who became a Photographer, known as the “Man of a million faces”. In 1994, their story was portrayed in a documentary. After Karl Swenson's death in 1978, Tompkins organized a group to help prospective Writers improve their narratives and to obtain publication of their works. She resided in Dana Point in Orange County, California, at the time of her death at the age of eighty-nine. She was survived by four stepsons from Swenson's first marriage. One is named Steven.