A device for assembling and locking floating box caissons, which includes, on the caissons faces to be assembled, a pre-locking system disposed at the corners of the caisson and comprising a lock-type male system on one caisson, and a hook-type female system on the other caisson. Such pre-locking system is designed for producing automatically the pre-locking of the assembled caissons. A manual positive locking system is disposed in the central positions of the caissons for completely locking the two caissons together.