Casparij made her debut for Heerenveen in the Eredivisie at the age of 15.[3] She made her league debut against Twente on 6 November 2015.[4] Casparij scored her first league goal against Achilles '29 on 23 December 2016, scoring in the 65th minute.[5]
VV Alkmaar
After two years, she moved to VV Alkmaar.[6] She made her league debut against Heerenveen on 1 September 2017.[7] Casparij scored her first league goal against Excelsior on 10 November 2017, scoring in the 45th minute.[8]
Second spell at Heerenveen
After a year at VV Alkmaar, she returned to Heerenveen.[9] During her second spell, she made her league debut against Achilles '29 on 14 September 2018.[10] She scored a hattrick, which was also her first goals for the club during her second spell, against Achilles '29 on 27 November 2018.[11]
Twente
She joined Twente in 2020.[12] Casparij made her league debut against Ajax on 6 September 2020.[13] She scored her first league goal against PEC Zwolle on 11 September 2020, scoring in the 82nd minute.[14]
Along with Rico Lewis, Casparij was named as the club's PFA Community Champions on 24 May 2024.[18]
International career
Casparij has played for Netherlands youth teams in several age groups. She made her senior team debut on 22 October 2021 as an 83rd-minute substitute for Daniëlle van de Donk in a 8–0 win against Cyprus.[19]