[3] During his years in the academy, he was chosen multiple times as the best player, such as at the 2002 Danone Nations Cup in France.
[5] During his time at Haarlem, Overtoom made 13 appearances for the first team, including his professional debut on 11 September 2009, in a 4–1 home loss to Helmond Sport.
In 2011, Ajax made the decision not to extend his expiring contract, and he departed the club as a free agent.
[10] On 21 June 2011, Overtoom signed a two-year contract with Eerste Divisie club Sparta Rotterdam.
[18] He made his debut for the club on 3 August 2013, the first matchday of the season, starting and providing an assist in a 3–2 away victory against Almere City, in which Robert Mühren scored a hat-trick.
[30] He made his debut for the club on 4 December, replacing Sven van Doorm in the 89th minute of a 2–1 home loss to Cambuur.