Propose: The thyroid hormones (T3, TSH, T4, and FT4) play a role in energy balance and regulation of energy expenditure. The aim present study to investigate the effect of moderate intensity aerobic training on thyroid hormone levels in inactive girls. Method: A total 30 inactive girls students were randomly selected and divided to training group (n=15) and control group (n=15). The training group doing research protocol for four week (three session per week of 70% maximal heart rate), also the control group was not intervened during the study. However, elevation anthropometric index before protocol training study. Blood samples were collected 24 hours before the first and after the last training session. For analysis data used T-test at significant level p<0.05. Results: Results showed a significant reduction of T3 (P<0.05), but no significant change were observed at T4, TSH, FT4 levels after training (P˃0.05). Conclusions: Our results showed that moderate aerobic training of 70% maximal heart rate have minimum effect on thyroid hormones in inactive adolescent girls.