We aimed to compare the efficacy of three tadalafil regimens for patients with type‐2 diabetes mellitus (DM), at least one microvascular complication and erectile dysfunction (ED). Sixty patients attending our urology clinic with erectile problems and diagnosed with ED, having DM for at least 5 years, and at least one microvascular complication linked to DM were identified and randomly divided into three groups—Group I: used 5 mg tadalafil daily, Group II: used 20 mg tadalafil 2 h before sexual relations twice a week and Group III: used 5 mg tadalafil daily and an extra 15 mg tadalafil 2 h before sexual relations twice a week. After treatment, the median International Index of erectile function (IIEF‐5) scores were significantly higher in Group III (15) compared to Groups I (8.5, p = 0.01) and II (9, p = 0.035). The groups were comparable in terms of the percentage of positive responses to the sexual encounter profile (SEP) 2 and the Global Assessment Questionnaires (GAQ)‐1. However, the percentage of patients with positive responses to SEP‐3 (20%, 40% and 75%, respectively) (p = 0.002) and GAQ‐2 (20%, 45% and 75%, respectively) (p = 0.002) was significantly higher in Group III. Therefore, using a combination treatment (daily 5 mg + 15 mg when needed) to treat erectile function in patients with DM‐related ED in the first stage may be more efficient with the same reliability and greater patient satisfaction.