Background: Methadone has long been regarded as an effective treatment for opioid dependence. However, many patients discontinue maintenance therapy because of its side effects, with one of the most common ones is erection dysfunction. This study aimed to determine and compare the effect of resistance training and lavender fragrances on erection function in men during methadone treatment of opioid dependence. Methods: This was an experimental study with pretest-posttest design and control group. The participants of the study were 50 married men aged between 30 and 45 years, who had gone to addiction treatment centers two week before. They were selected via convenience sampling method and were allocated to four groups of resistance training, lavender, combination (resistance training and lavender), and control after being matched on the basis of age and history of addiction. Resilient and combined training group participated in resistance training sessions for 24 sessions (8 weeks, 3 sessions a week). Lavender and combination group smelled lavender for 21 sessions of 20 minutes. Before and after the intervention, the data were collected using the erectile function of men questionnaire. Data were analyzed using ANCOVA test. Findings: All three types of intervention; resistance training (P = 0.002), lavender (P < 0.001), and combination group (P < 0.001) improved erection function significantly. In addition, using lavender fragrances had a better effect on erection function compared to resistance training (P = 0.003). Conclusion: It is recommended to use resistance training and fragrances to improve sexual function in men during methadone treatment of opioid dependence.