Lori Martin was born Dawn Catherine Menzer, in Glendale, California, at 10:02 a.m.; her fraternal twin sister, Doree, arrived four minutes later. As she weighed only 5 pounds and measured just 18 inches at birth, she spent the first few weeks of her life in an incubator, during which time her survival was somewhat doubtful. Her father, Russell C. Menzer (1916–1999), was an MGM and Warner Brothers commercial Artist and art Director. She had a younger brother, Stephen Menzer, and an older sister, Jean Coulter, a veteran Hollywood stuntwoman who doubled for Barbara Anderson on Ironside, and Farrah Fawcett and Cheryl Ladd on Charlie's Angels, sometimes Kate Jackson and Jaclyn Smith.

As well as appearing in several commercials, including one for which her father designed the set and a Milky Way candy commercial, she won parts in the films Machine-Gun Kelly (1958), The FBI Story (1959), and Cash McCall (1959). She appeared in several television series, including Medic, Wagon Train, Alfred Hitchcock Presents, Leave It to Beaver, and Whirlybirds.

At the age of 12, Martin was the 975th young hopeful to be auditioned for the role of Velvet Brown in the NBC television version of National Velvet, the role for which she is best remembered. After being included in the final three, she was interviewed ten more times before winning the part. Ann Doran played her mother, Martha Brown; Arthur Space, her father, Herbert Brown. When she won the role, her name was changed from Dawn Menzer to "Lori Martin". On the change of name, Martin later said that, "I didn't like the name Lori at first. But I like it now. The reason I like it now is I've been brainwashed!" The show ran for fifty-eight episodes between 1960 and 1962.

In 1962, Martin won the role of Nancy Bowden in the film Cape Fear, which also starred Gregory Peck, Polly Bergen, and Robert Mitchum. Martin later said that she delivered her best performance as Nancy but had nightmares for weeks after the filming of the scene in which her character is stalked by Mitchum's character. The Director of the film, J. Lee Thompson, originally wanted Hayley Mills for Martin's part. Because he could not get Mills, however, he later admitted to having deliberately given Martin a hard time during filming.

Lori jumped on the singing teen idol bandwagon and released her only single on Bob Keane's legendary Del-Fi Records. Recorded at Radio Recorders in Hollywood in September 1963, the girl group-styled "The Home of the Boy I Love", backed with "Mine 'Til Monday" (Del Fi 4201), was mistakenly released with songwriting credits given to the successful team of Barry Mann and Cynthia Weil when in fact it was produced by Barry Mann and written by lesser known hit-man Sylvester Bradford. Bradford's claim to fame was his composition of "Tears On My Pillow", which was a #4 hit in 1958 for Little Anthony & The Imperials. Although Lori Martin's only record went nowhere fast, it has now become quite collectable and sought after among girl group record Collectors.

During the early 1970s, Martin decided to put her acting career on hold. She later recalled that her reasoning behind her decision was that "I'd been in the Business long enough to know I'd been stereotyped. My mother was in poor health and I felt I had worked from such an early age I could take some time off and get a college education." A few years later, she tried to reactivate her career but unfortunately she became "discouraged by the many changes in casting and techniques".

Martin married Charles Breitenbucher, had a son, Brett, and moved to Westlake Village, California, under her married name, Dawn Breitenbucher. She later moved to Oakhurst, California. She occasionally attended autograph signings and ran a medical supplies company with her husband until his death in 1999. In February 2008, she participated as an election worker when the people of Oakhurst voted on whether the community should become incorporated or not. During that campaign she gave an interview to the local ABC television station..

Lori Martin, known legally as Dawn Breitenbucher, died on April 4, 2010, in Oakhurst, California, two weeks before her 63rd birthday, from undisclosed causes. She was survived by her son, Brett Breitenbucher, and her siblings, Doree Thompson Kelly, Jean Marek and Stephen Menzer, as well as extended family.