Belgian international utility defender Thomas Vermaelen won five major trophies during his time at Dutch Eredivisie giants Ajax Amsterdam during his time at the club. Thomas Vermaelen was at Germinal Beerschot in his native Belgium before he joined the Ajax Amsterdam youth team.

Thomas Vermaelen made his debut for the Ajax Amsterdam first team during the win over FC Volendam on February 15, 2004. He celebrated his professional debut with a win thanks to the 2-0 away victory over FC Volendam. He won the first of his five major trophies at Ajax during that season. Vermaelen was part of the Ajax Amsterdam squad that won the league title at the end of the 2003/04 Dutch Eredivisie season.

Vermaelen was in the Ajax Amsterdam squad that beat rivals PSV Eindhoven to win the 2005/06 Dutch Cup. Ajax made it 16 Dutch Cup titles by beating PSV 2-1 in the final with Klaas-Jan Huntelaar getting both goals.

Thomas Vermaelen scored one of the successful Ajax Amsterdam penalties during the dreaded penalty shootout as they beat AZ Alkmaar 8-7 on penalties in the final to win the 2007/08 Dutch Cup title after the two teams played out a 1-1 draw. Huntelaar was on target again for Ajax Amsterdam during that final, while Moussa Dembele scored the goal for AZ Alkmaar.

Belgian defender Vermaelen won the 2006 Dutch Super Cup and the 2007 Dutch Super Cup titles with Ajax Amsterdam. Vermaelen played the whole game as Ajax beat PSV Eindhoven 3-1 to win the 2006 Dutch Super Cup with the likes of Mauro Rosales, Kenneth Perez and Wesley Sneijder on target.

Vermaelen also featured for the whole game as Gabri scored just before the half-time break to give Ajax Amsterdam a 1-0 win over PSV Eindhoven. The slim win over PSV gave Ajax Amsterdam the 2007 Dutch Super Cup title.