Born in Rotterdam, Koolwijk began his senior career with Excelsior during the 2007–08 season. He signed for NEC in May 2011.[4] He also played for Dordrecht and AS Trenčín,[1][5] before returning to Excelsior in May 2016.[6] He returned to Trenčín in June 2019 and became a regular in the team's starting eleven.[7] In April 2020, when the Fortuna Liga was suspended due to the COVID-19 pandemic in the country, Koolwijk ended his contract with the club by mutual agreement, as he intended to spend more time with his family in the Netherlands and he was dissatisfied by the proposed salary cut of over 50%, due to the pandemic.[8] He signed with Almere City in May 2020.[9]
He signed for PEC Zwolle in September 2021.[10] After a season, which ended with relegation to the 2022–23 Eerste Divisie, 36-year old Koolwijk announced his retirement from football, as he had accepted a job offer as assistant coach of the Suriname national team.[11]