Clooney, 56, took a night off from watching their twins and looked delighted to be out and about.
Matt Damon, 46, dressed smartly along with his wife Luciana, 40, who wore a fitted dress that hugged her body.
The famous party is in Italy for the 74th annual Venice Film Festival. Concerns had been raised recently with how thin Amal was looking.
Clooney is busy preparing for the October premiere of his new thriller Suburbicon which he is directing, that stars Julianne Moore, Matt Damon and Oscar Isaac.
Commenting on the arrival of his twins, Ella and Alexander, three months ago the actor said "'Right now my job is changing diapers and walking them around a little bit. I really didn't think at 56 that I would be the parent of twins."
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