The invention relates to a device for treating the hair, comprising: - a first (5) and a second arm (6) connected together by a joint (8) and able to move with respect to one another between a closedconfiguration for treating the hair and a spread configuration for engaging between them the hairs to be treated, - a removable refill (20) comprising a body having a housing, a member for applying acosmetic product received in the housing, the refill (20) comprising at least one first mounting means (27) engaging with at least one second mounting means (29) of the first arm (5), in such a way that the assembly of the first and second mounting means (27, 29) is performed by moving the first mounting means (27) along an axis (Y) substantially parallel to the joint (8), relative to the second mounting means (29).