The unique and interactive effects of mirrored exercise environments and the presence of co-exercisers on sedentary women's exercise-induced feeling states (FS) were examined. Participants (n = 92; mean age = 20.2) performed 20 min of moderate intensity exercise in one of four environments: (a) alone/mirrored, (b) not alone/mirrored, (c) alone/unmirrored, or (d) not alone/unmirrored. FS were measured pre-, mid-, and 5 min post-exercise. Self-consciousness, perceived social evaluation and social comparisons were also assessed post-exercise. Multilevel modeling procedures indicated that women in the not alone/mirrored environment experienced smaller increases in post-exercise revitalization than the other conditions (p < 0.05), and were the only condition to experience increased physical exhaustion (p < 0.05). Women in the not alone/mirrored condition also reported greater self-consciousness and more social comparisons than those in alone/mirrored condition (ps < 0.01). Findings are consistent with Objective Self-Awareness Theory, and suggest that mirrored, group exercise environments are not conducive to psychological well-being among women unaccustomed to exercise.