Deputies from the Sheriff's Office responded to her Sausalito, California, home around 9:30 p.m. Monday after receiving a report of a possible cardiac arrest.
Shakur was transferred to a hospital where she died about an hour later, at 10:28 p.m.
The Sheriff's coroner will lead an investigation into the cause and manner of Shakur's death.
Shakur, who was born in North Carolina and became a Black Panther and activist, was the subject of her late son's 1995 hit song "Dear Mama," in which he detailed his childhood struggles and love for his mother.
Tupac Shakur was shot Sept. 7, 1996, in Las Vegas, Nevada, and died in the hospital six days later from his injuries. His assailant was never caught.
After his death, Afeni Shakur formed the Tupac Amaru Shakur Foundation, and in 2014 helped create the Broadway musical "Holler If Ya Hear Me," featuring the rapper's music.
She was also an executive producer for the film "All Eyez on Me," about her son's life. The film is set to be released in November.