"Appalled by the horrific attack in Nice. I strongly condemn such mindless acts of violence. My thoughts are with the families of deceased," Modi said in a tweet on Friday morning.
At least 80 people were killed on Thursday night when a large truck mowed through a crowd celebrating Bastille Day in Nice.
French President Francois Hollande said the truck attack was of a "terrorist character".
Modi hoped for early recovery of the injured people. Over 150 people were injured in the mayhem.