Something of a footballing nomad, at club level, Toni played for twelve different Italian teams throughout his career. A late bloomer, he spent several seasons in the lower divisions of Italian football, as well as promising spells with minor Serie A clubs Vicenza and Brescia, before finally making his breakthrough with Palermo: he helped the team to Serie A promotion during the 2003–04 season by winning the Serie B title, and was the league's top scorer with 30 goals; the following season, he helped the club qualify for Europe, scoring 20 goals in Serie A. After two prolific seasons with Fiorentina, Toni also spent three seasons with German side Bayern Munich, where he helped the club to a domestic treble during the 2007–08 season, also reaching the UEFA Cup semi-finals; after falling out with the club's manager during his third season with the team, and being demoted to the reserve squad, he later returned to Italy on loan with Roma in 2010, and subsequently had spells with Genoa and Juventus. In 2012, he played for Al-Nasr Dubai SC, in the UAE Arabian Gulf League, but returned to Fiorentina for a season later that year. He retired in 2016, after three seasons with Verona, the last as team captain.
At international level, he represented the Italian national team on 47 occasions, scoring 16 goals. He made his international debut in 2004 and took part at the 2006 FIFA World Cup, UEFA Euro 2008, and the 2009 FIFA Confederations Cup with Italy; he most notably contributed to Italy's 2006 World Cup victory, as he scored twice and was elected to the tournament's All-star team.
A prolific goalscorer, Toni scored over 300 goals throughout his career, and is one of the top-five highest scoring Italians in all competitions. In addition to the team medals he has collected, he also won several individual honours: during his first spell with Fiorentina, he won the Capocannoniere (Serie A top scorer) award during the 2005–06 season, in which he scored 31 goals (the most goals in a Serie A season since 1958–59), which also earned him the European Golden Shoe, becoming the first Italian player ever to win the award; he was also the league's joint top scorer in the 2014–15 Serie A season, in which he became the oldest player to win the award at the age of 38, with 22 goals. Toni also finished as top scorer in the 2007–08 Bundesliga, with 24 goals, and in the 2007–08 UEFA Cup, with 10 goals.
After retiring in 2016, Toni worked with the Italian national team as a "de facto" coach, and was officially appointed as Under-21 manager in March 2017.