A juvenile vehicle seat includes a seat shell having a seat bottom and a back support coupled to the seat bottom. A headrest of the juvenile vehicle seat is coupled to the seat shell for up-and-down movement relative to the seat shell to adjust a height of the headrest above the seat bottom of the seat shell. The juvenile vehicle seat further includes a height-adjustment mechanism arranged to adjust the height of the headrest above the seat bottom. The height-adjustment mechanism is arranged to move between a locked position to prevent up-and-down movement of the headrest and an unlocked position to permit up-and-down movement of the headrest.