Background: A systematic review on low-level light/laser therapy (LLLT) in male pattern hair loss (MPHL) and female pattern hair loss (FPHL) has been performed. Objectives: Compare the reported effectiveness of LLLT in MPHL and FPHL with any control, through randomized controlled trials (RCTs) analysis. Methods: The protocol was developed in accordance with the Preferred Reporting for Items for Systematic Reviews and Meta-Analyses-Protocols guidelines. A multistep search of the PubMed, MEDLINE, Embase, PreMEDLINE, Ebase, Clinicaltrials.gov, Scopus database, and Cochrane databases has been performed to identify articles on MPHL and/or FPHL treatment with LLLT. Results: Of the 298 articles initially identified, 136 articles focusing on MPHL and FPHL were selected and, consequently, only 36 articles focused exclusively on LLLT. Of this amount, 23 articles were clinical trials while 13 articles were systematic reviews. Systematic reviews were excluded, and only seven articles were analyzed as RCTs. Conclusions: All the articles selected and analyzed reported a positive effect of LLLT for MPHL and/or FPHL treatment without side effects.