The purpose of this study was to investigate the effect of optical flow velocity in a virtual reality (VR) environment on user's postural control. We hypothesized that the velocity of the optical flow will perturb user's balance indicated by an increase center of pressure (COP) distance travelled and speed. Seventeen young, healthy participants were tested in one-foot support stances. Our study showed the visual perturbations increased COP distance in one-foot support and the slowest perturbation velocity induced the highest response. For VR communities, developers could use this information to raise their awareness that any sudden shift in the virtual environment at any velocity could reduce a user's postural stability and place them at risk of falling, particularly at slower perturbation velocities.