Tamoxifen is an off-label option to treat men for breast cancer, infertility, and idiopathic gynecomastia. Lately, tamoxifen has been proposed as a treatment to prevent gynecomastia in prostate cancer patients receiving antiandrogen therapy. We reviewed the adverse events (AEs) reported in studies of men prescribed tamoxifen for these conditions to better understand its side-effect profile. We searched PubMed for randomized controlled trials (RCTs) that included safety data of tamoxifen treatment in men with prostate cancer, breast cancer, infertility, and idiopathic gynecomastia. Non-RCTs were also reviewed. The results demonstrate that the AE profile in tamoxifen-treated male populations varied. Excluding breast events, gastrointestinal, and cardiovascular problems were the most commonly reported AEs in prostate cancer patients, whereas more psychiatric disorders were reported in male breast cancer patients. Few AEs have been documented in men receiving tamoxifen for infertility and idiopathic gynecomastia. Less than 5% of men withdrew from tamoxifen therapy because of toxicity. This suggests that for most men, tamoxifen is well-tolerated. Of those who discontinued tamoxifen, the majority were male breast cancer patients, and cardiovascular events were the most common reason for stopping tamoxifen treatment. Unfortunately, in many cases, the reasons for withdrawing tamoxifen were unspecified. Based on the available evidence, tamoxifen's AE profile appears to vary depending upon which male population is treated. Also, the frequency at which AEs occur varies - less AEs in men with infertility and idiopathic gynecomastia compared to men with prostate cancer or breast cancer. Long-term studies that rigorously document the side-effect profile of tamoxifen in men are lacking.