Montgomery was born in Winnipeg, Manitoba. She is the daughter of actor Cecil Montgomery. Her siblings are actor Lee Harcourt Montgomery and actress Tannis G. Montgomery. She began acting in teen roles, including the 1967 family series Barney Boomer, and 1969 television special Hey, Cinderella! playing the role of Cinderella.
During the 1970s, Montgomery played many leading roles in made-for-television movies, including D.A.: Conspiracy to Kill (1971), Lock, Stock and Barrel (1971), The Bravos (1972), Women in Chains (1972), and The Devil's Daughter (1973). She made her big screen debut in the 1971 thriller film The Todd Killings opposite Robert F. Lyons. She later starred in the romantic drama film The Other Side of the Mountain (1975) and its sequel The Other Side of the Mountain Part 2 (1978), and the crime dramas Breaking Point (1976) and Stone Cold Dead (1979). In 1984, she starred in the slasher film Silent Madness.
In the early 1970's, Montgomery began to be credited as Belinda J. Montgomery. As she explained in October 1977 to Indianapolis News columnist Richard K. Shull:
I was told five years ago, If I kept my name as it was, I would have lots of accidents, I'd be accident prone. I had a lot of brushes with accidents – landing gear collapsing on an airplane – so I added my middle initial and things have been better. It's in the numerology.
Montgomery starred alongside Patrick Duffy in the short-lived NBC science fiction series Man from Atlantis from 1977 to 1978. In 1988, she starred in another short-lived NBC series, Aaron's Way. From 1989 to 1993, she starred as Katherine Howser, Doogie's mother, in the ABC medical comedy-drama series, Doogie Howser, M.D.. Montgomery also had a recurring role on the Miami Vice, and has made over 80 guest appearances on television, including appearances on Ironside, T. J. Hooker, Dynasty, The Love Boat, Murder, She Wrote, L.A. Law, JAG, Mannix, Magnum, P.I., The Sixth Sense, The Virginian and Ghost Whisperer, among other series. Her recent credits include 2010 action film Tron: Legacy and 2017 Lifetime Christmas romantic comedy Snowed-Inn Christmas.
In March 2013, writing under the pen name B. Montgomery, Belinda submitted a short story "St. Patrick of the Pineapple" to Midlife Collage, an online writing contest. Montgomery's story won first place in the contest.
