Postural control is fundamental to balance and to movements such as gait, and it matures gradually through childhood. Balance-board intervention may improve static and dynamic balance by enhancing proprioceptive and sensory integration, but its acute effects on static balance and on gait remain unclear. This study investigated the acute effect of a single session of two balance boards, a multidirectional wobble board and a wide-based lateral rocker board, on static balance and dynamic gait stability in typically developing children and young adults. A randomized crossover design was used, and three-dimensional motion capture and force-plate data were collected before and after each session. Static postural control was assessed from center-of-pressure (COP) during single-leg standing in 15 adults and 14 children, and dynamic gait stability was assessed during an obstacle-crossing task in 12 adults and 12 children through spatiotemporal parameters, lower-limb joint kinematics, and the margin of stability (MoS). Results showed that children had greater COP values than adults on all static measures (all p < .001) and prevalent differences in gait, maintaining larger AP MoS but a smaller ML MoS at foot-off than adults. Neither board reduced COP, and the only static interactions were found for ellipse height (p = .029) and ML COP range (p = .025) reflecting a slight increase in adults. During gait, the intervention produced a small, board-specific effect consistent with task specificity. The AP MoS shifted toward greater stability from pre to post on the rocker board but not the wobble board. There was a single age-dependent change in trailing-limb ankle dorsiflexion (group by time interaction, p = .043). Overall, a single balance-board session did not acutely improve static single-leg balance with either board, or its effect on dynamic gait stability was limited to a small, direction-specific gain in AP stability under the rocker board. The findings suggest that acute balance-board effects are task-specific and direction-specific particularly rocker board's ML-oriented influence, and a single session may be insufficient to induce substantial postural changes in both children and adults.