An auxiliary seat (1) attachable to a pushchair (2) to enable it to accommodate two children seated side-by-side. The seat comprises a frame (10) having a backrest (22) and a base (21) and a wheel (30) in contact with the ground in an operative position. A child seated on the base is supported with their back against the backrest (22). The frame (10) is configured so that the backrest (22) and the base (21) fold substantially flat when the auxiliary seat is not in use. The auxiliary seat (1), including the base (21) and backrest (22), can pivot relative to the pushchair (2) to be folded against the side thereof in a storage position with the wheel (30) off the ground, once the base (21) and the backrest (22) of the seat have been folded substantially flat.