The present invention discloses an accessory and an infant seat having the accessory. The accessory includes a main body, an engaging portion and an operating member. The engaging portion is disposed on the main body and has a locking position for engaging with the infant seat and a releasing position for disengaging from the infant seat. The operating member is slidably disposed on the main body and is connected to the engaging portion. The operating member is operated to slide for switching the engaging portion between the locking position and the releasing position. The accessory moves the engaging portion to the locking or releasing position via sliding of the operating member, so that the accessory can be engaged with or detached from the infant seat. The accessory is convenient to operate and has a simple structure and a low manufacturing cost.