A juvenile seat includes a base having a bottom seat portion, a lower back section coupled to the base and positioned to lie at an angle relative to the bottom seat portion, and a headrest coupled to the lower back section for up and down movement relative to the base and the lower back section. The juvenile seat also includes a height-adjustment mechanism coupled to the headrest for up and down movement with the headrest to adjust the height of the headrest above the bottom seat portion. The height-adjustment mechanism is movable between a locked position to prevent up and down movement of the headrest relative to the lower back section and an unlocked position to permit up and down movement of the headrest relative to the lower back section.