Aim: The aim of the study was to compare the effectiveness of dienogest (DIE), depo medroxyprogesterone 17-acetate (MPA), and micronized progesteron (MP) regimens for treatment of simple endometrial hyperplasia (EH) without atypia. Methods: One hundred and twenty premenopausal patients aged between 35 and 55, with simple EH without atypia, were offered 3 types of progestins (MPA, MP, and DIE) and were randomized to one of them. After 6 months of treatment, patients were reevaluated. The efficacy of different progestins in treatment of EH was compared with regard to resolution and regression rates. We classified the terms of resolution and regression as “complete response” and persistence as “no response”. Results: A total of 99 patients continued the study (31 in MP, 35 in MPA, and 33 in the DIE group). None of the results of endometrial pathology were progressed to atypia or complex hyperplasia. The complete response resolution rate was 93.5% in the MP, 88.5% in the MPA, and 96.9% in the DIE group. The highest complete response rate was in the DIE group, although there was no statistically significant difference between groups (p = 0.39). The efficacy of progestins was similar between the groups. Conclusion: DIE is an effective and convenient method for thinning the endometrium.