The present invention relates to a collar (1) for pets, the collar (1) comprising a tightening structure consisting of a buckle (2) having a first projecting structure (21) formed longitudinally on the top (23a) and a second projecting structure 22a formed transversely to the center of the bottom (23b) of the buckle (2), the first and second projecting structures (21, 22a) facing one another without touching.