An infant highchair includes a standing frame including a support platform, a seat pivotally connected with the standing frame and having a seating surface, and a locking mechanism operable to lock the seat in position. The seat is rotatable between a first and a second position, the first position allowing a child to sit in contact with the seating surface, and the second position being suitable to receive installation of a removable child seat over the seat while disabling seating of a child on the seating surface, the seating surface moving around the support platform when the seat rotates relative to the standing frame, the second position of the seat uncovering the support platform so that a removable child seat is installable over the seat at least partially supported in contact with the support platform. The locking mechanism is operable to lock the seat in the first and second position.