On 14 January 2013, he signed a pre-contract deal with Vitesse.
On 2 July, it was announced that Leerdam signed a three-year deal with the Arnhem club.
On 1 August 2013, Leerdam made his Vitesse debut in their UEFA Europa League qualifier tie against Petrolul Ploiești, in which Leerdam featured for the entire 90 minutes during the 1–1 draw.
Three days later, Leerdam scored on his league debut for Vitesse in their 3–1 home victory over Heracles Almelo, netting the opener in the 27th minute.
Leerdam went onto score eight times in total during the 2013–14 campaign and started to attract interest from Vitesse's feeder club, Chelsea during January 2014.

During the 2015–16 campaign, Leerdam was dropped by interim-manager Rob Maas for the foreseeable future after the full-back discredited Vitesse in a recent interview.
Leerdam therefore, failed to feature again for Vitesse until the following campaign, when Rob Maas was replaced by Henk Fraser.
On 31 March 2017, it was announced that Leerdam would leave Vitesse along with Arshak Koryan, Wouter Dronkers and Ewout Gouw at the end of their current deals in June 2017.

He played as Vitesse won the final of the KNVB Beker 2–0 against AZ Alkmaar on 30 April 2017 to lead the club, three-time runners up, to the title for the first time in its 125-year history.
On 14 January 2013, he signed a pre-contract deal with Vitesse. On 2 July, it was announced that Leerdam signed a three-year deal with the Arnhem club. On 1 August 2013, Leerdam made his Vitesse debut in their UEFA Europa League qualifier tie against Petrolul Ploiești, in which Leerdam featured for the entire 90 minutes during the 1–1 draw. Three days later, Leerdam scored on his league debut for Vitesse in their 3–1 home victory over Heracles Almelo, netting the opener in the 27th minute. Leerdam went onto score eight times in total during the 2013–14 campaign and started to attract interest from Vitesse's feeder club, Chelsea during January 2014.
During the 2015–16 campaign, Leerdam was dropped by interim-manager Rob Maas for the foreseeable future after the full-back discredited Vitesse in a recent interview. Leerdam therefore, failed to feature again for Vitesse until the following campaign, when Rob Maas was replaced by Henk Fraser. On 31 March 2017, it was announced that Leerdam would leave Vitesse along with Arshak Koryan, Wouter Dronkers and Ewout Gouw at the end of their current deals in June 2017.
He played as Vitesse won the final of the KNVB Beker 2–0 against AZ Alkmaar on 30 April 2017 to lead the club, three-time runners up, to the title for the first time in its 125-year history.
Kelvin Leerdam