The collision occurred at around 2.10pm on the Muckross Road or N71, between Muckross House and the Torc Waterfall in Killarney.
The motorcyclist, a man aged in his 20s, was airlifted to Cork University Hospital where he remains in a serious condition. The driver of the car was uninjured.
A technical examination of the scene has since been carried out.
Gardaí are appealing for anyone who may have witnessed the collision – particularly any road users who may have camera footage – to contact them.
Anyone with information can contact gardaí in Killarney on 064 667 1160 or the Garda Confidential Line on 1800 666 111.