The Ocean's Eleven actor hurt his leg when a Mercedes car allegedly turned without giving right of way and collided with his scooter, Italian press agency AGI said.
Clooney, 57, was reportedly thrown from his two-wheeler on to the windscreen of the vehicle in Costa Corallina on the island's northeast coast at around 8 am. The car driver called an ambulance which took Clooney to hospital, AGI added.
His wife Amal, a human rights lawyer, rushed to Clooney's side in hospital, according to local newspaper La Nuova Sardegna, who reported he was later discharged and advised to follow a course of physiotherapy.
A CAT scan revealed no broken bones, just minor trauma to one knee, Italian news agency Ansa said.
Photo: Alex Macbeth
The north-east coast of Sardinia is popular with the rich and famous, although Clooney is on location on the island to film a new mini-series, Catch 22.
AGI said part of the road was closed following the collision. Police told AFP they were unable to comment while operations related to the crash were still under way.
Clooney broke a rib in a motorcycle accident in New Jersey in 2008, while his then-girlfriend Sarah Larson suffered a broken foot.
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Photo: Pierre Teyssot/AFP