Born at Mantua, Boninsegna started his career in Serie B (the second tier of Italian professional football) with Prato in 1963–64 season. He transferred to Potenza, who was Serie B team in 1964–65 season. He also played for Varese in 1965–66 and Cagliari between 1966–1969, helping the club to a second-place finish during the 1968–69 Serie A season alongside Luigi Riva. During the summer of 1967, Cagliari came to the United States to play in the North American Soccer League as the Chicago Mustangs; Boninsegna led the club in scoring with 11 goals in nine matches. Boninsegna gained a status as an efficient striker with Internazionale Milano F.C. and the Italian national football team in the 1970s, playing alongside Sandro Mazzola. In Serie A, he totaled 171 goals in 281 games, and was top goalscorer in Italy during the 1970–71 and 1971–72 Serie A seasons, with Inter.