With regard to European competition, Willem II first appeared in UEFA Cup Winners' Cup of 1963 where they lost to Manchester United in the first round by an aggregate score of 7–2. In 1998–99, Willem once again competed in the Cup Winners' Cup and after beating Dinamo Tbilisi of Georgia 6–0 in both legs, Willem then lost to Spanish side Real Betis in the second round, 4–1 on aggregate. A second place in the Eredivisie of 1999 guaranteed the club a UEFA Champions League berth for the first time. At the tournament's group stage, Willem only attained two points in their six group G matches and were thus eliminated. After reaching the KNVB Cup final in 2005 where they lost 4–0 against PSV Eindhoven, Willem II again qualified again for the UEFA Cup, in which they lost to French side AS Monaco in the first round by 5–1 on aggregate.
At the end of the 2010–11 season, Willem II were relegated from the Eredivisie for the first time in 24 years. In the 2011–12 season under new manager Jurgen Streppel Willem II was promoted back to the Eredivisie, but they went right back down the next season after finishing bottom of the table. The club became champions of the Eerste Divisie in the subsequent season and were thus promoted back to the Eredivisie.
In early 2015, journalists at De Volkskrant revealed that Willem II had its matches fixed by an "Asian gambling syndicate", who had paid Willem's players a total sum of €100,000 to lose matches against Ajax and Feyenoord (in October and December 2009). According to the journalists, midfielder Ibrahim Kargbo was the Asians' main contact within the club; Kargbo denies having accepted their money. The Royal Dutch Football Association called the affair "the most concrete case of match fixing in the Netherlands" and took legal action as well as asking UEFA and FIFA to reevaluate previous matches.
In 2019, Willem II reached the KNVB Cup Final for the fourth time in their history. They beat AZ Alkmaar in the semi-finals after a penalty shoot-out, but were defeated by in the final by AFC Ajax.
The fans of Willem II have close links with the fans of English championship club Bristol City. Willem supporters have been known to travel to Bristol, with Bristol City fans heading the other way to Tilburg. At Bristol City's game on 31 October 2009 against Sheffield Wednesday, some Willem II fans were seen in the 'Eastend' of the Ashton Gate Stadium, and songs were sung about Willem II by City fans.
As of 24 July 2021
Note: Flags indicate national team as defined under FIFA eligibility rules. Players may hold more than one non-FIFA nationality.