During the 2008–09 Dutch football season, AZ Alkmaar competed in the Eredivisie, playing their 42nd season of competitive football (Alkmaar '54 and FC Zaanstreek had merged to form AZ in May 1967).

AZ were knocked out of the KNVB Cup in the quarterfinals suffering a 2-1 home loss to NAC Breda, although they did secure a notable 1-0 (aet) win over PSV Eindhoven in the third round.

van Gaal left the club at the end of the season to join FC Bayern Munich and was succeeded by Ronald Koeman.

Note: Flags indicate national team as defined under FIFA eligibility rules; some limited exceptions apply.

Note: Flags indicate national team as defined under FIFA eligibility rules; some limited exceptions apply.