Patients with major presentations of alopecia experience physically harmful effects and psychological comorbidities, such as depression and anxiety. Oral minoxidil (OM) has been suggested by dermatologists as a potential remedy; however, its effectiveness remains unclear. This systematic review aims to collate published studies and to analyze the effect of OM among patients diagnosed with any type of alopecia. For this systematic review, Medline/PubMed, Cochrane Central, EMBASE, Web of Sciences, and Latin American and Caribbean Health Sciences Information System were searched for relevant studies from inception to September 21, 2019. Of 1960 studies retrieved in several electronic databases and three additional records identified though reference list from potentially eligible studies, nine studies (one randomized controlled trial and eight nonrandomized controlled trials) met the requirements and were used in our analysis. Although we found positive effects in favor of OM, this should be interpreted cautiously due to very low quality of the evidence of outcomes in the selected studies. Definitive conclusions are not possible without high-quality trials. This review has highlighted the absence of high-quality randomized controlled trials evaluating OM in the treatment of various types of alopecia. Given the mild adverse events of OM, future studies should also analyze doses and duration to maximize efficacy and decrease side effects.