A seat for children intended to be installed in a vehicle, in particular an automobile, comprising a seat bottom, a seat back, and a headrest, the headrest is mobile in translation relatively to the seat back between a lost position and a high position. The seat includes a child-restraint harness intended to maintain a child seated in the seat and configured to include two shoulder straps, each of the shoulder straps carrying a strap-receiving pad adapted to contact a child seated on the seat bottom.