In August 2020, it was announced that Kooij was to join UCI WorldTeam Team Jumbo–Visma midway through the 2021 season, after spending the first part of the season with the Jumbo–Visma Development Team; he signed a contract until the end of the 2023 season.[10] The following month, he won the opening stage of the Settimana Internazionale di Coppi e Bartali in a sprint finish, ahead of Ethan Hayter and Phil Bauhaus.[11]
In February 2021, Team Jumbo–Visma announced that Kooij would make an immediate move to the World Tour Team, thus becoming the first teenager cyclist to have a full season contract with the team since its creation.[4]
Major results
2018
1st Overall La Coupe du Président de la Ville de Grudziądz
^"David Dekker wint de zestigste Ster Van Zwolle" [David Dekker wins the 60th Ster van Zwolle]. Wielerflits (in Dutch). Wielerflits BV. 29 February 2020. Retrieved 29 August 2020. Olav Kooij werd tweede, voor titelverdediger Coen Vermeltfoort die door zijn vele aanvalspogingen tekort kwam voor de dagwinst. [Olav Kooij came in second, ahead of defending champion Coen Vermeltfoort who came up short for the win on the day, due to his many attacking attempts.]