Marshall was born on April 9, 1929, in Brooklyn, New York, the child of Barbadian immigrants who were among the first wave of Caribbean islanders to relocate to the United States. Her early life was suffused with Caribbean culture; she spoke its language and followed many of its traditions. Marshall made her first visit to the Caribbean when she was nine years old, which inspired her to write poetry. After graduating from high school in 1949, she attended Brooklyn College (now part of the City University of New York). She graduated with a bachelor of arts degree in English literature in 1953 and became a Phi Beta Kappa member.

From 1953 to 1956, Marshall worked as a researcher and journalist for the African-American magazine Our World. Her job required her to travel to Brazil and the Caribbean. While attending graduate school at Hunter College, which she entered in 1955, she started writing her...