Classical ballet involves the performance of complex movements that require high-level motor skills and good postural control. This study explored postural sway in passé en demi-pointe position in dancers and compared single-leg standing sway (with and without visual restriction) between dancers and non-dancers. Fourteen professional dancers and 14 sex- and age-matched volunteers who were not ballet dancers participated in the study. Participants stood on a force plate on the dominant leg in the following positions: 1. single-leg stance with eyes open (reference task) and with eyes closed and blindfolded for 35 seconds; and 2. passé en demi-pointe position with eyes open for 20 seconds (dancers only). The center of pressure signal was used to calculate the following variables: average velocity; anteroposterior and mediolateral velocity peaks; anteroposterior and mediolateral displacement ranges; average displacement; and ellipse area. Significant interaction effects (p < 0.001, η2 = 0.419) were observed between groups and postural tasks, with higher stabilometric values for the dancer group during the single-leg stance with eyes closed and blindfolded task, as evidenced by the average displacement of 241.0 cm in dancers and 147.1 cm in non-dancers (p = 0.025), and by the ellipse area of 9.5 cm2 for dancers and 4.9 cm2 for non-dancers (p = 0.001). In regard to the positions with eyes open, an increase was noted only in the average sway velocity and mediolateral velocity in passé en demi-pointe position compared with the single-leg stance with eyes open (p < 0.001). Greater postural sway might be interpreted as the result of either inadequate postural stability or exploratory behavior to maintain postural stability in more challenging tasks. It is concluded that professional ballet dancers show greater visual dependency for balance adjustment with reduced influence of the supporting base on postural sway.