DeCamp first came to fame in November 1937, when she took the role of Judy Price, the secretary/nurse of Dr. Christian in the long-running radio series of the same name. She also played in The Career of Alice Blair, a transcribed syndicated soap opera that ran in 1939-1940. She made her film debut in Cheers for Miss Bishop and appeared in many Warner Bros. films, including Eyes in the Night, Yankee Doodle Dandy playing Nellie Cohan opposite James Cagney, This Is The Army playing the wife of George Murphy and the mother of Ronald Reagan, Rhapsody in Blue and Nora Prentiss. She played the mother of the character played by Sabu Dastagir in Jungle Book. In 1951 and 1953, respectively, she starred in the nostalgic musical films On Moonlight Bay and its sequel, By The Light Of The Silvery Moon, as Alice Winfield, Doris Day’s mother, opposite Leon Ames. DeCamp played Peg Riley in the first television version of The Life of Riley opposite Jackie Gleason in the 1949–1950 season, then reprised the role on radio with original star William Bendix for an episode of Lux Radio Theater in 1950. From 1955–1959 she was a regular on the popular NBC television comedy The Bob Cummings Show, playing Margaret MacDonald,[4] widowed sister of Cummings’s character, the womanizing photographer and former World War II pilot Bob Collins; Dwayne Hickman (the future star of The Many Loves of Dobie Gillis) portrayed her son, Chuck. DeCamp had a recurring role as Helen Marie, the mother of Marlo Thomas on That Girl, from 1966–1971 on ABC. She appeared in several episodes of the CBS sitcom Petticoat Junction as Kate Bradley’s sister, Helen, filling in as a temporary replacement for the ailing Bea Benaderet as the mother figure to Bradley’s three daughters.

She appeared in the 1961 Rawhide episode, “Incident Near Gloomy River”. In 1962, she appeared as a dishonest Southern belle in the NBC sitcom Ensign O’Toole with Dean Jones. She appeared in the role of Gertrude Komack on ABC’s medical drama Breaking Point in the episode entitled “A Little Anger is a Good Thing”. She played the mother of Shirley Partridge in “The Partridge Family.” She also played The Fairy Godmother in the 1980s TV show, “The Memoirs of a Fairy Godmother”. DeCamp delivered a short but memorable performance as Hannah Bailey, wife of the hardy, cantankerous pioneer James Briton “Brit” Bailey (Paul Fix) in the 1969 episode “Here Stands Bailey” of the syndicated television series Death Valley Days, hosted by Robert Taylor not long before Taylor’s own death. In the story line, the Baileys make their final settlement in southeastern Texas after having overcome many obstacles over the years. Now they face the order of Stephen F. Austin (John Carter) that they vacate their land. Austin soon has a change of heart and asks them to stay. Bailey dies with his final wish of interment standing upright facing west, hence his grave marker, “Here Stands Bailey Facing West.” In 1965, DeCamp plaed the newspaper editor Caroline Romney of Durango, Colorado, in the episode, “Mrs. Romney and the Outlaws”. In the story line, Romney sounds the alarm for citizens to fight the Kimball/Sykes gang. Willard Sage played Marshal Christy. During the 1960s, she appeared in commercials for the laundry product 20 Mule Team Borax, which sponsored Death Valley Days. DeCamp played Buck Rogers’ mother in flashback scenes of the Buck Rogers in the 25th Century episode “The Guardians” (1981). On July 7, 1946, her Beverly Hills home was damaged when struck by a wing after the experimental XF-11 piloted by Howard Hughes (re-created in the 2004 movie, The Aviator) crashed nearby. A piece of the wing and a part of the neighbor’s roof landed in DeCamp’s bedroom, where she and her husband were sleeping; they sustained no injuries.

DeCamp was married to Inglewood Municipal Judge John Ashton Shidler from 1941 until his death in 1998. The Shidlers raised four daughters: Margaret, Martha, Valerie, and Nita. Outliving most of her contemporaries, DeCamp died of pneumonia in 2001. She was ninety years of age.