BACKGROUND: Walking on an incline demands specific neuronal control because the vestibular system may alter gait patterns to maintain balance with respect to self-orientation to gravity. A previous study confirms the aforementioned hypothesis that walking on inclines with bilateral vestibular disruptions altered spatial-temporal gait parameters in anterior-posterior and vertical directions. This study extended the current knowledge to investigate bilateral mastoid vibration's effect on the Margin of Stability (MoS) while walking on inclines. METHODS: Eighteen healthy young adults participated in this study. Participants were randomly assigned to eight treadmill trials, encompassing walking at their preferred walking speed on inclines of 0%, 3%, 6%, and 9% with and without bilateral mastoid vibrations. The dependent variables were MoS in both the anterior-posterior (MoSap) and medial-lateral (MoSml) directions, the variability of MoS in both AP (MoSVap) and ML (MoSVml) directions, step length, step length variability, step width, and step width variability. RESULTS: We found the significantly greater MoSap (3%: p = 0.005, 6%: p = 0.002, 9%: p <
0.001) and the significantly larger step length (3%: p = 0.008, 6%: p = 0.025, 9%: p <
0.001) while walking on different inclines with bilateral mastoid vibration than without vestibular stimulation. We also noticed MoSml (F DISCUSSION: These results revealed that bilateral mastoid vibrations impact the margin of stability in both directions, and walking on inclines requires adjustment of MoS. This result may facilitate future clinical implications for patients with compromised vestibular functions.