Alessandro played 91 times for the Italian national team between 1995 and 2008, scoring 27 goals. He played in three FIFA World Cup finals – 1998, 2002 and 2006 - and four UEFA European Championships – 1996, 2000, 2004 and 2008.

His greatest moment for Italy was the 2006 World Cup where he scored the second goal in a 2–0 semi-final win over hosts Germany. In the final against France, which ended 1–1 after extra time, Alessandro scored a penalty in the shoot-out as Italy won the tournament for the fourth time. He said afterwards that winning the World Cup was his childhood dream.

He played as a support striker, often filling the space between midfield and forwards, a position known in Italy as the ‘trequartista’. He displayed vision, creativity and the ability to beat opponents, providing the assist for many goals. He was also a free kick specialist.

His greatest days in club football were when he was a player for Juventus for 19 years - 11 of which were as captain. He holds the Juventus club record for goals scored (290) and appearances (705). He was a member of the Juventus team which won the Serie A championship in 1995, 1997, 1998, 2002, 2003 and 2012. Juventus also won the Champions League in 1996, beating Ajax on penalties in the final.

Alessandro was named in the FIFA 100, a list of the greatest living footballers selected by Pelé as a part of FIFA's centenary celebrations. He was also voted in the list of best European players for the past 50 years in the UEFA Golden Jubilee Poll.

In September 2012, he signed a two-year deal with Sydney, reputedly becoming the highest-paid footballer ever to play in the A-League. In 2014 he played for Delhi Dynamos for a short period in the Indian League, before retiring in October 2015.

He became a Laureus World Sports Academy Member in March 2016.