Born in England, Belmore moved to the United States in 1910 where she settled, achieving citizenship in 1939 and fame as a leading stage actress, as well as on film.

She first visited the United States in 1910 to appear in the musical comedy Our Miss Gibbs, produced by Charles Frohman and would later work with William Faversham.

Belmore helped arrange acting classes in Shakespearean drama for Nellie Bramley, an upcoming Australian stage actress.

In June of 1935 she starred in a joint production of the Vine Street Theatre and Harold Lloyd's Beverly Hills Little Theatre for Professionals, "The Widow in Green," directed by Dickson Morgan, and also starring Grace Stafford, Alden Chase, Colin Campbell, and Viola Moore.

Belmore was born on 30 June 1874[2] and baptised on 27 September 1874 in St Marylebone, Westminster, England as Daisy Gertrude Garstin.

[4] Belmore did not believe she resembled her mother and in her opinion, took after her father who was a prominent comedian and acted alongside his friend Sir Henry Irving.

Afterward, her mother doubted her future on stage, fearing she lacked the necessary voice and talent, and warned that continuing might disgrace the family name.

[8] She came to the United States in 1910, having sailed from Southampton, England and arriving in New York on 29 July 1910[9] to appear in the musical comedy Our Miss Gibbs, which was produced by Charles Frohman.

[4] In 1921, Belmore achieved significant acclaim for her role as Old Sweetheart in Three Live Ghosts, where she portrayed a "gin drinking lovable old mother"[4] with such skill that she received widespread praise.

[11] For this role, she dramatically altered her appearance, so much so that she was unrecognisable to those who had seen the play, leading to concerns that people might mistake her stage disfigurement for her actual looks.

[17] Outside of films, Belmore was also a theatre actress, having directed and toured for 40 weeks with The Vagabond King, primarily in Chicago.