Purpose: A systematic review of the use of peer assessment in Physical Education in the last five years (2016–2020). Method: Four databases were used to select those articles that included information on peer assessment in Physical Education in the different educational stages. According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, including the PICO (participants, intervention, comparators, and outcomes) strategy, after the exclusion criteria, 13 articles were fully assessed based on seven criteria: (1) year and author; (2) country; (3) educational stage; (4) type of paper; (5) purpose; (6) content; and (7) outcomes. Results: the results show that the research was geographically dispersed, although Spain and the USA had half of the articles reviewed. The research was carried out at all educational stages, although a greater focus was observed in higher education than in primary and secondary education. Quantitative, qualitative, and mixed research was almost equally represented, and dealt mainly with sports and games. Regarding the goals of the studies, a diversity of research so great that it produced a lack of continuity and coherence in the literature on the subject was found. The research results on the use of peer assessment showed an increase in the level of motivation, perceived teaching confidence and competence, and teaching self-efficacy. More research is needed on the benefits of the use of peer assessment on the self-regulation of learning and the critical thinking of students.