Born in New York, New York, Furness began her professional career as a model before being signed to a film contract by RKO Studios. Her first film role was as the "Thirteenth Woman" in the 1932 film Thirteen Women but her scenes were deleted before the film's release. Over the next few years she appeared in several RKO films, and became a popular actress. Among her film successes were Magnificent Obsession (1935) and the Fred Astaire and Ginger Rogers film Swing Time (1936). By the end of the decade she had appeared in over forty films, but during the 1940s found it difficult to secure acting roles.

In 1948 she was performing in the television series Studio One which was broadcast live. She filled in for an actor to promote Westinghouse products during the advertisement break, and impressed the company with her easy and professional manner. They offered her a contract to promote their products and she subsequently became closely associated with them. One of television's most recognizable (and occasionally parodied) series of commercials had Furness opening wide a refrigerator door, intoning, "You can be sure... if it's Westinghouse." (Ironically, Furness may be best known today for a commercial in which she did not appear: during a live spot for Westinghouse, a refrigerator door failed to open, creating one of the most infamous bloopers in TV history. This actually did not happen to Furness, as has often been claimed, but to another actress who was subbing for her.)

She was a regular panelist on What's My Line? in 1951, and that fall appeared in a series of live mysteries on ABC, under the weighty title Your Kaiser Dealer Presents Kaiser-Frazer "Adventures In Mystery" Starring Betty Furness In "Byline". In 1953 she appeared in her own television series Meet Betty Furness which was sponsored by Westinghouse and she remained a spokesperson for the company until 1960. She then attempted to move into a less commercialized role in television but found herself too closely associated with advertising to be taken seriously. During this time she worked on radio, and also on behalf of the Democratic Party.

In 1967 President Lyndon Baines Johnson, aware of her work for the Democrats contacted Furness and offered her a position as Special Assistant for Consumer Affairs. She accepted the assignment and continued in this role until the end of the Johnson administration in 1969. During her tenure she silenced her critics by applying herself studiously to her role and learning the issues relating to consumer rights. She headed the Consumer Affairs Departments of both New York City, and New York State from the late 1960s before returning to television.

Signed by WNBC in New York, Furness reported on consumer issues, and specifically targeted examples of consumer fraud. In 1976 she began an association with The Today Show filling in as anchor, and providing regular reports. In 1977 her program Buyline: Betty Furness won the Peabody Award.

In 1990 she was diagnosed with cancer. She continued working for The Today Show until she was released from her contract in 1992. Her dismissal was widely publicised and controversial and was viewed by many of Furness' supporters as ageism.

She had always expressed throughout her life that her philosophy was to never turn down a job, and she stated that it was this attitude that had allowed her to progress through such an unconventional series of professions. During her illness she stated that she wanted nothing more than to be able to work, but her health continued to deteriorate until her death in New York from stomach cancer.

Betty Furness has two stars on the Hollywood Walk of Fame for her contribution Motion Pictures, and to Television.