Mary Jeanette Robison was born on 19 April 1858 in Moama, New South Wales, Australia, in what Robson described as "the Australian bush". She was the fourth child of Henry and Julia Robison; her siblings were WIlliams, James, and Adelaide.

Henry Robison (1810-1860) was born in Penrith, Cumberland, England and lived in Liverpool. He served 24 years in the foreign trade of the British Merchant Navy as a mate and a sea captain. Robison retired at half-pay due to his poor health and traveled with Julia Robison to Melbourne, Victoria, Australia in 1853 on the SS Great Britain. By April 1855, Henry was a watchmaker, jeweller, silversmith and ornamental hairworker in Melbourne. According to Robson, her parents both suffered from phthisis pulmonalis, and moved to "the bush" for their heath. Henry bought a large brick mansion in Moama, New South Wales in August 1857 and opened the Prince of Wales Hotel. From there, he co-operated Robison and Stivens, coach proprietors for the Bendigo - Moama - Deniliquin Service. The hotel was Robson's first home. Henry Robison died in Moama Maiden's Punt on 27 January 1860.

On 19 November 1862, Julia married Walter Moore Miller, solicitor and mayor of Albury, New South Wales at St Paul's Cathedral, Melbourne. Julia, Walter, and the four children moved to Melbourne in 1866. Miller was a partner with De Courcy Ireland in the firm of Miller and Ireland in Melbourne in November 1867, and until 20 January 1870, when it was mutually dissolved.

In 1870, the family moved to London. Robson attended Sacred Heart Convent School at Highgate, north London and studied languages in Brussels. She went to Paris for her examinations in French. According to her obituary, Robson was also educated in Australia.

Robson ran away from home to marry her first husband, 18 year-old Charles Leveson Gore, in London. They were married on 1 November 1875 at the parish church in Camden Town, London. The couple traveled on the steamer SS Vaderland and arrived in New York on 17 May 1877. The Gores purchased 380 acres of land in Fort Worth, Texas where they built a house and established a cattle ranch. According to Jan Jones, "the Gores survived two years in their prairie manor house before homesickness, rural isolation, and repeated bouts of fever convinced them to sell and try their fortunes in the more settled east." They moved to New York City with little money and Robson says that shortly after, Gore died.

On 17 September 1883, she became an Actress in Hoop of Gold at the Brooklyn Grand Opera House stage. Her name was incorrectly spelled "Robson" in the billing, which she used from that point forward "for good luck". Over the next several decades, she flourished on the stage as a Comedian and character Actress. Her success was partly due to her affiliation with powerful manager and Producer Charles Frohman and the Theatrical Syndicate. She established her own touring theatrical company by 1911.

Six years after beginning her stage career, Robson married Augustus Homer Brown, a police surgeon, on 29 May 1889. They remained together until his death on 1 April 1920. Robson's son, Edward Gore, was her Business manager.

She appeared as herself in a cameo in the 1915 silent film, How Molly Made Good. Robson starred in the 1916 silent film A Night Out, an adaptation of the play she co-wrote, The Three Lights.

In 1927, Robson went to Hollywood where she had a successful film career as a senior aged woman. Among her starring roles was in The She-Wolf (1931) as a miserly millionaire businesswoman based on the real-life miser Hetty Green.

She also starred in the final segment of the anthology film If I Had a Million (1932) as a rest home resident who gets a new lease on life when she is given a $1,000,000 check by a dying Business tycoon. She played the Queen of Hearts in Alice in Wonderland (1933), Countess Vronsky in Anna Karenina (1935), Aunt Elizabeth in Bringing Up Baby (1938), Aunt Polly in The Adventures of Tom Sawyer (1938), and a sharp-tongued Granny in A Star Is Born (1937). Robson was top-billed as late as 1940, starring in Granny Get Your Gun at age 82. Her last film was 1942's Joan of Paris.

In 1933, Robson was nominated for an Academy Award at age 75 in the Best Actress category for Lady for a Day but lost to Katharine Hepburn; both actresses appeared in the Hepburn-Grant classic film, Bringing Up Baby.