Born Rina Faccio in Alessandria, Piedmont, she was forced to drop out of school at 16 and marry the man who raped her.

Her first book described her decision to leave her husband and son and move to Rome, which she did in 1901. She became active in political and artistic circles. During this time she writes extensively on feminism and homosexual understanding.

In 1908, she met Cordula "Lina" Poletti at a women's congress, and their one-year lesbian relationship formed the basis for the novel Il passaggio. Poletti was described as being beautiful and rebellious, and was prone to wear men's clothing. She is sometimes credited with being one of the first women in Italy to openly flaunt her lesbianism. Poletti would later become involved with actress Eleanora Duse.

Sibilla Aleramo would go on to be one of Italy's leading feminists. Her personal writings to Poletti have, in more recent years, been studied due to their open minded views toward homosexual relationships. While Aleramo was involved with Poletti she was also in love with a man, Giovanni Cena. Aleramo expresses in her letters to Poletti that she never felt guilt for having loved both of them at the same time.

In later life Aleramo toured the continent and was active in Communist politics after World War II. The 2002 film Un Viaggio Chiamato Amore depicts Aleramo's affair with writer Dino Campana.