When the two waiters are running to the Mafia in the restaurant, the left-hand waiter's hair color is black; in the next take, his hair is gray.
When Madame Souza, pretending to be blind, is following the mechanic, she approaches a junction where there is a fire hydrant, a newspaper vending machine, and a pedestrian crossing. In the next shot, all have vanished.
Near the end, where the Triplets and Souza are going across the bay over the bridge, a ship passes under it entering the harbor. However, when the Mafia goes over the edge into the funnel of the ship, it is leaving the harbor, not entering it.
The odds on the chalkboard when cyclist #2 falls off his bike.