Introduction: Changes in myostatin levels and modulation of body composition may help explain the adaptation of these variables in response to exercise. Therefore, the present study was conducted with the aim of comparing the effect of two methods of training, namely, resistance training (RT) and functional training (FT) on myostatin and body composition in sedentary men. Materials and Methods: In this semi-experimental study, with a pre-test-post-test design and a control group, 45 sedentary men in Isfahan in 2022 were selected based on convenient sampling and were randomly divided into three groups: FT (n= 15), RT (n= 15) and control (n= 15). Both training programs were performed for 8 weeks, three sessions per week, and took 40 to 50 minutes each session. . Blood sampling for the measurement of the myostatin and measuring the percentage of body fat (BF%) and lean body mass (LBM) were done in two phases: pre-test and post-test. The data were analyzed using the Covariance and Bonferroni post hoc tests. Results: The results of study showed that both training methods had significant effects on decreasing myostatin and BF% and increasing LBM in non-active men (p<0. 001). However, these changes of variables were higher in the FT group than in the RT group (p<0. 05). Conclusion: These results showed the effect of both training methods on decreasing myostatin and BF% and increasing LBM,although these changes were more in FT. Therefore, it is recommended, coaches, athletes and other officials involved in sport exercises use these training methods, especially FT, for the progress of sport performances and improvement of body composition.