Aging is accompanied by postural instability and gait impairments, increasing the risk of falls in older adults. Research in motor control and learning consistently demonstrates that attentional focus strategies significantly influence motor performance, including postural control and balance during walking. This study aimed to investigate the effects of attentional focus strategies on dynamic gait stability. Nineteen healthy older women (Age:60.7±6.4 years) participated after providing written informed consent. Participants walked along a 5−meter pathway under three conditions: normal walking, internal focus, and external focus. A 30−cm obstacle was positioned 2 meters from the starting point, and gait kinematics were recorded after obstacle crossing using the smartphone−based motion capture system OpenCap. Dynamic postural control during walking was assessed using the Margin of Stability (MoS), a validated measure of dynamic gait stability. MoS was calculated as: MoS=BoS-(X_CoM+V_CoM/√(g/l)), where center of mass position (XCoM) and base of support (BoS) were derived from a scaled musculoskeletal model in OpenSim software, and CoM velocity (VCoM) was computed via time differentiation. Gravity acceleration (g) and CoM height (l) were incorporated, with calculations performed in MATLAB. MoS was evaluated in anterior-posterior and medio-lateral directions. Statistical analysis employed Repeated-measures ANOVA with Bonferroni post-hoc tests. The results demonstrated significantly greater dynamic stability in the anterior–posterior direction during the external focus condition compared with the internal focus condition (p=0.01). In addition, the comparison between normal walking and internal focus approached statistical significance (p=0.07). No significant differences were observed in medio-lateral stability across conditions. These findings suggest that external focus can enhance gait stability in older adults following a balance challenge (obstacle crossing), whereas internal focus may compromise stability. Therefore, rehabilitation and fall-prevention programs are encouraged to incorporate external focus strategies while avoiding explicit instructions directing attention toward body movements in order to optimize gait stability in aging populations.