At the 2008 Summer Olympics in Beijing she won a gold medal with the 4×100 m freestyle relay. She did so alongside Inge Dekker, Ranomi Kromowidjojo and Marleen Veldhuis in a time of 3:33.76, just 0.14 outside their own world record. The day after she competed individually in the 200 m individual medley where she finished 28th during the heats. Heemskerk was the lead-off swimmer in both 4×200 m freestyle and 4×100 m medley relays, both of which did not qualify for the finals.