Born in Rome, since young age Tamantini studied piano, singing and classical dance at the Teatro dell'Opera di Roma. In 1948 she was chosen by Luchino Visconti to play Olimpia in the stage drama Rosalinda o come vi piace, and one year later she made her film debut in Fernando Cerchio's Cenerentola, a musical adaptation of the Charles Perrault's fairy tale Cinderella