On 17 October 2008, Eriksen signed a two-and-a-half-year contract with Amsterdam-based club, Ajax. The transfer fee received by OB was estimated at €1 million (£847,199) while Middelfart also received a sum of €35 000 which they later used to construct a football pitch. He worked his way through the youth teams at Ajax and was promoted to the first team squad in January 2010, where he was given the number 51 shirt. Later that month, he made his first team debut in a 1–1 Eredivisie with NAC Breda. He scored his first goal for Ajax on 25 March in a 6–0 win over Go Ahead Eagles in the Dutch Cup and extended his contract with the club the following month. On 6 May, he played in the second match of the final of the 2009–10 Dutch Cup as Ajax beat Feyenoord 4–1, prevailing 6–1 on aggregate. At the end of his first professional season with the club, Eriksen had played 21 competitive matches, scoring one goal, and had made his international debut for Denmark. Eriksen's form throughout the campaign earned praise from manager Martin Jol who compared him to former youth products Wesley Sneijder and Rafael van der Vaart as well as Danish legend, Michael Laudrup for his reading of the game in the traditional number 10 role.
