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Background and Objective: Limited studies have been conducted on the effect of resistance training plus protein supplements on weight control, muscle growth and body composition. The purpose of this study was to evaluate the effects of a whey protein supplement combined with a 6-week strength training on weight loss, body composition, strength, and muscle hypertrophy in overweight young men. Materials and Methods: Thirty individuals with a body mass index between 25-30 kg/m2 participated in the study. They were randomly divided into three groups of 10 persons each as follows: 1. Experimental group 1 (whey supplement + 6 weeks of strength training (W) 2. Experimental group 2 (placebo + 6 weeks of strength training (D) 3. Control group (C). Maximum strength and muscle volume of the subjects were measured by the 1-RM test in bench press, biceps curl, Squats and chest, arm and tight limb. Skinfold thickness (triceps, supraillium, abdomen and thigh) were measured with Lange skinfold calipers. Repeated measure ANOVA and Bonferroni post hoc test were used for data analysis. Results: No significant changes occurred in body weight and BMI (p>0.05). The waist-to-hip ratio (WHR) also remained unchanged in all groups (p>0.05). In both the experimental and placebo groups significant reductions in percent body fat and fat mass and significant increases in the lean body mass, strength, and muscle hypertrophy were observed (p<0.05) after 6 weeks of strength training. Conclusion: Strength exercise training alone increases strength, hypertrophy and muscle mass and improves body composition in sedentary, overweight young men. Our results suggest that protein supplementation is not needed for strength improvement or body composition changes. Keywords: Whey protein isolate, Strength training, Weight loss, Body composition, Overweight