Mafai left school very early, preferring to attend, with Scipione, the Scuola Libera del Nudo, or free school of the nude, of the Accademia di Belle Arti di Roma. His influences in those years were Roman galleries and museums, and the Fine Arts Library at Palazzo Venezia.
He met painter and sculptor Antonietta Raphaël in 1925, and they married. In 1927 Mafai exhibited for the first time, with a show of studies and maquettes organised by the Associazione Artistica Nazionale in Via Margutta. In 1928 he had a second exhibition, at the XCIV Mostra degli Amatori e Cultori di Belle Arti, as well as a collective with Scipione and other painters, at the Young Painters Convention of Palazzo Doria in 1929.