Karsavina was born in St. Petersburg, Russia, the daughter of the dancer Platon Karsavin. Beautiful and talented from an early age, Karsavina quickly moved through the ranks of professional ballet. After graduating from the Imperial Ballet School, she was a leading ballerina of Tsar's Imperial Ballet, dancing the whole of the Marius Petipa repertory. Her most famous roles were Lise in La Fille Mal Gardée, Medora in Le Corsaire, and the Tsar Maiden in The Little Humpbacked Horse. She was the first ballerina to dance in the so-called Le Corsaire Pas de Deux in 1915.
The choreographer George Balanchine said he had fond memories of watching her when he was a student at the Imperial Ballet School. It was during the late 1910s that she began traveling regularly to Paris to dance with the Ballet Russe of Sergei Diaghilev. It was during her years with the company that she created many of her most famous roles in the ballets of Mikhail Fokine, including Petrushka, and Le Spectre de la Rose. She was perhaps most famous for creating the title role in Fokine's The Firebird (a role originally offered to Anna Pavlova, who could not come to terms with Stravinsky's score) with her occasional partner Vaslav Nijinsky.
She left Russia in 1919 after the revolution, and subsequently continued her association with the Ballet Russe as a leading Ballerina. (Her brother Lev Platonovich Karsavin moved to newly independent Lithuania, where he acquired a university chair in cultural history; when the Soviets occupied Lithuania in 1940, he was arrested and died in a gulag.)
Her memoirs, Theatre Street, discusses her training at the Imperial Ballet School, and her career at the Mariinsky Theatre and the Ballet Russe. Tamara Karsavina was renowned for her beauty, and in the ultra-competitive world of ballet, she was almost universally beloved. However Karsavina did have a rivalry with Anna Pavlova. In the film A Portrait of Giselle Karsavina recalls a "wardrobe malfunction": during one performance her shoulder straps fell and she accidentally exposed herself, and Pavlova reduced an embarrassed Karsavina to tears.
In 1917 she married diplomat Henry James Bruce and moved to London, where she taught and wrote about ballet. Among her pupils were two prima ballerinas assoluta, Dame Alicia Markova (the first British dancer to hold the rank of Prima Ballerina) and Dame Margot Fonteyn. Although married, she did have a brief affair with notable Hollywood socialite and writer Mercedes de Acosta. The two were as much friends as they were lovers, and Karsavina was one of the few who continued to be friendly toward de Acosta following the controversial autobiography released by the latter, exposing many of her (de Acosta's) lesbian relationships with Hollywood's elite to the public.
She retained her beauty into old age, and at the end of her life could reduce a crowded room to admiring silence merely by the manner of her entering it. Scandalously under-used by the management of the Royal Ballet, she occasionally assisted with the revival of the ballets in which she danced, notably Spectre de la Rose, in which she coached Margot Fonteyn and Rudolf Nureyev. In 1959 she advised Sir Frederick Ashton on his important revival of La Fille Mal Gardée for the Royal Ballet, in which she taught the him Petipa's original mimed dialogue for the celebrated scene When I'm Married, as well as his choreography for the Pas de Ruban - two passages which are still retained in Ashton's production.