During his Serie A club career, Bertini played for several Italian teams: Empoli (1963–64), Fiorentina (1964–68), and most notably Inter Milan (1968–77), where he remained for nine seasons, winning the Scudetto in 1971; he had previously also won a Coppa Italia and a Mitropa Cup double with Fiorentina in 1966.

[1] He missed out on the 22-man Italy squad for the 1966 FIFA World Cup, although he was still brought to England by manager Edmondo Fabbri, along with Luigi Riva, as an additional reserve in order to gain experience with the national side.

[2] Bertini played in the 1970 FIFA World Cup, where he wore the number 10 shirt,[3] as Italy managed a second-place finish.

In the final, he marked Pelé in his movements in depth outside the area, although Brazil eventually defeated Italy 4–1.

[4] A quick, well-rounded, and hard-working defensive midfielder, Bertini was mainly known for his stamina, strength, and tackling abilities, and was also capable of playing as a defender due to his defensive attributes; although he primarily served as a ball-winner, he was a complete midfielder who was also known for his eye for goal from midfield, due to his powerful striking ability from distance, as well as his accuracy from penalties and ability to make later attacking runs from behind into the penalty area.