His second novel, At Night All Blood is Black, was inspired by his Senegalese great-grandfather's silence about his experiences in World War One.
The £50,000 prize will be split between Diop and the book's translator - US author and poet Anna Moschovakis.
It fended off competition from five other shortlisted titles, including Éric Vuillard's The War of the Poor.
The International Booker Prize is awarded every year for a single book that is translated into English and published in the UK or Ireland.
