Emergency services and Loch Lomond rescue boat volunteers were called to the scene near Boturich shore and Balloch Park at about 17:00 on Thursday.
The volunteer team assessed the man’s injuries and transferred him by stretcher onto a lifeboat. Meanwhile, the jet ski was secured by a park ranger patrol boat.
Paramedics took the man into their care, and he was taken to hospital. Rescuers left the scene at about 18:10.
It follows a warning to jet ski riders from the Loch Lomond & The Trossachs National Park Authority on Thursday.
The park authority said it would increase patrols this weekend in an attempt to stamp out a rise in what it called “dangerous, reckless and aggressive behaviour”.
The Loch Lomond byelaws, which were strengthened in 2023, are intended to ensure safe and responsible use of the loch via speed-restricted areas and other measures.
