Boninsegna made his debut for Italy on 18 November 1967, in an away UEFA Euro 1968 qualifying match against Switzerland, which ended 2–2, although he was not called up for the final tournament, which Italy ended up winning on home soil under manager Ferruccio Valcareggi, with whom he would have several disagreements throughout his international career. With the national side, he took part in two World Cups, the first in 1970, and the second in 1974. In total, he managed 9 goals for Italy in 22 appearances.