Daily stair activities have become increasingly challenging for older adults with deterioration in physical and cognitive capabilities. However, the dynamic stability of older adults during stair descent under a concurrent dual-task condition remains undetermined. The gait and dynamic stability variables of 40 healthy older adults were measured under single- and dual-task conditions during stair descent. The step length, step width, and single support time did not significantly increase (p > .05) under the dual-task condition during stair descent. The medial–lateral center of mass velocity significantly increased (p < .003), whereas the medial–lateral margin of dynamic stability value significantly decreased (p < .006) at the landing and initial single support under the dual-task condition during stair descent. The self-regulatory ability of healthy older adults under the dual-task condition during stair descent was underestimated. Dual tasking displayed a positive impact on the anterior–posterior dynamic stability of healthy older adults.