The John Paul II hospital in Olbia said the actor was released on Tuesday.
Local media that had gathered at the hospital said Clooney is believed to have left through a side exit.
The 57-year-old had been heading to a film set on Tuesday when his motorbike was hit by a car, according to local daily La Nuova Sardegna.
Private media firm Mediaset, citing gossip magazine Chi, said the accident occurred near Costa Corallina, in the province of Olbia.
Clooney has a home on the Italian mainland, on Lake Como.