We conducted a post-marketing observational study to investigate the safety and effectiveness of eldecalcitol for the treatment of osteoporosis in a Japanese clinical setting. The observation period was 12 months for women and 36 months for men. The final results for the female patients have already been published. In this article, the final results for the male patients are reported. A total of 470 male osteoporosis patients were enrolled. The safety analysis set included 431 patients (mean age, 76.8 years; mean ± SD follow-up period, 631.0 ± 450.3 days), and 175 patients continued treatment throughout the 3-year observational period. Adverse drug reactions (ADRs) were reported in 28 patients (6.49%); the most common ADRs were hypercalcemia (1.16%) and renal impairment (1.16%). Serious ADRs were reported in 5 patients (1.16%). Mean serum calcium was within the normal range throughout the observation period. The cumulative incidence of new vertebral and nonvertebral fractures at 36 months, estimated by Kaplan-Meier analysis, was 10.23 and 4.06%, respectively. At the last observation, mean lumbar spine bone mineral density was 3.49% higher (P < 0.0001) than at baseline, and levels of the bone turnover markers BAP and TRACP-5b were reduced (-14.64%; P = 0.0009, and - 29.51%; P < 0.0001, respectively). In conclusion, the safety and effectiveness of eldecalcitol for the treatment of Japanese male osteoporosis patients was confirmed in clinical practice. Careful monitoring of serum calcium and estimated glomerular filtration rate, both before and during treatment, is necessary to minimize the risk of hypercalcemia and renal impairment while maximizing the effectiveness of eldecalcitol.