Born in 1909 Modiba was a cabinetmaker. While a youngster in the Tzaneen district, he refused to tend the sheep of a European cattle farmer and received eight cuts. Modiba came to Johannesburg in 1926 and worked as a domestic servant and later in textile and garment factories. In June 1955, he served as an African National Congress (ANC) delegate at the Congress of the People in Kliptown.