After spending time at VK Tielrode and Germinal Beerschot, Vertonghen moved to the Netherlands and signed a contract with the youth academy of Eredivisie side Ajax. He began as a midfielder but now he mostly plays at centre back for Ajax. During his time in the reserves, he became known for an incident in the 2006 KNVB Cup game against Cambuur Leeuwarden, his first ever home game at the Amsterdam ArenA, where he "scored" a bizarre goal to put Ajax 3–0 up. He had attempted a back pass to the Cambuur goalkeeper while a teammate was receiving treatment but instead the ball sailed past the shocked goalkeeper, much to the amusement of the spectators and the bewilderment of the players.