For her contribution to motion pictures, she has a star on the Hollywood Walk of Fame at 1724 Vine Street in Hollywood.

Born in Shreveport, Louisiana, Minter was the younger of two daughters born to Joseph "Homerun" Reilly (1877–1958) and Lily Pearl Miles (later known as Broadway Actress Charlotte Shelby; 1877–1957). Her sister was Margaret Reilly, who later became an Actress using the name Margaret Shelby.

In her screen debut, in which she was billed as Juliet Shelby, she appeared in the 1-reel drama short The Nurse (1912). From there her new stage name was applied and Minter was starred in the role as Viola Drayton, the fairy, in the 5-reel feature length drama The Fairy and the Waif (1915).

As is Common with many silent movie stars, much of Minter's work has been lost; she made 53 films, approximately a dozen of which are known to exist today. A print of her 1919 movie, The Ghost of Rosy Taylor surfaced in New Zealand in the 1990s. Other known surviving movies include The Fairy and the Waif (1915), Youth's Endearing Charm (1916), A Dream or Two Ago (1916), Innocence of Lizette (1916), The Eyes of Julia Deep (1918), Nurse Marjorie (1920), A Cumberland Romance (1920) and The Little Clown (1921).

The ensuing scandal, following the Roscoe "Fatty" Arbuckle scandal of Labor Day weekend 1921, and Arbuckle's subsequent murder trial, was the subject of widespread media speculation and embellishment. Newspapers reported that coded love letters written by Minter had been found in his bungalow after his death (these were later shown to have been written three years earlier, in 1919). Minter was at the height of her success, having starred in more than 50 films, and newspaper revelations of the 20-year-old star's association with the 49-year-old murdered Director was cause for a sensational scandal.

In late 1922, several months following Taylor's death, Minter became romantically involved for a time with then-news correspondent of Los Angeles and movie critic Louis Sherwin, who had at one time been married to Actress Maude Fealy.

Minter made four more motion pictures for Paramount, with her last being The Trail of the Lonesome Pine (1923). When the studio did not renew her contract, she received many other offers but declined them all, saying she had never been happy as an Actress.

In 1925, Minter sued her mother for an accounting of the money Shelby had received for her during her screen career. The case was settled out of court, with the settlement being signed by Minter and Shelby at the American Consulate in Paris, France, on January 24, 1927.

There were several suspects (including her mother, Charlotte Shelby) in the long investigation of Taylor's murder. In 1937, Minter publicly announced to the Los Angeles Examiner newspaper, "Now I demand that I either be prosecuted for the murder committed fifteen years ago, or exonerated completely. If the District Attorney has any evidence, he should prosecute. If not, then I should be exonerated... Shadows have been cast upon my reputation." Taylor's murder was never solved.

Minter commented she was content to live without her Hollywood career. She later reconciled with her mother and proclaimed her love for Taylor throughout her life. Minter's money had been invested in Los Angeles real estate and she seems to have lived in relative comfort and prosperity. She later moved to a house in Santa Monica, California; her mother, Charlotte Shelby, died there in 1957.

In a 1970 interview, during which she described Taylor as her "mate," Minter recalled going to view Taylor's body immediately after the murder. In shock, she demanded to be used for a blood transfusion to revive him, not believing he was dead until she touched his body in the morgue: “That deadly cold... convinced me as nothing else could have done. No life can return to this man.” She broke down and sobbed: “They crucified Jesus. Now they’ve crucified... They’ve crucified my mate.”

In 1981, Minter was severely beaten in a burglary at her home in which more than $300,000 worth of antiques, china and jewelry were taken. A former live-in companion and three other people were later charged with attempted murder and burglary. The police described her as a frail old woman and people were often shocked to learn she had once been a famous movie star.

Mary Miles Minter died in 1984, at age 82, from a stroke in Santa Monica. She was cremated and her ashes were scattered at sea.