Background and Objectives: Most research on the effects of exercise on body image has concentrated on the benefits of regular exercise. However, some research has indicated that exercise has an immediate impact on body image. The aims of this study were to investigate the immediate effects of aerobic exercise in a fitness class and the at-home environment on body image, and to examine the impact of nutritional status (i.e., normal weight vs. overweight/obesity) and exercise addiction on these changes. Method: 322 Hungarian women participated in the study with two different environmental conditions, fitness class condition (N = 155) and at-home video condition (N = 167). They completed the Body Appreciation Scale and Exercise Addiction Inventory before and after a one-hour aerobic exercise session. Self-report data on weight, height and exercise frequency were also collected. Results: There were no significant differences between the fitness class and video groups in terms of age, educational level, BMI, body appreciation, exercise frequency and exercise addiction. We found that 7.5% (N = 24) of the participants were at risk for exercise addiction. Aerobic exercise had a significant positive effect on body appreciation (t(321) = 7.564, p < .001) independently from environment and nutritional status. Exercise addiction moderated the relationship between exercise and body image, the at risk for exercise addiction group showed the greatest improvement (F(1) = 3.252, p = .040). Conclusion: The results indicate that even a one-hour aerobic exercise session has a positive effect on body image; this has important practical implications for intervention strategies and weight-loss treatments.