The association between polycystic ovary syndrome (PCOS) and metabolic syndrome (MetS) is not widely recognized or properly assessed in adolescents. The aim of this study was to conduct a systematic review and meta-analysis to provide reliable results concerning MetS development in adolescents with PCOS. We searched studies published in PubMed, Medline, and Web of Science from January 2010 to December 2020. The quality of studies was assessed by the Newcastle–Ottawa Scale (NOS), and the data analysis was performed with Stata 14.0. Twelve articles were finally included in the systematic review and meta-analysis. The results suggested that adolescents with PCOS have more than three times the odds of having MetS than controls (OR 3.32, 95% CI [2.14, 5.14]). Obese adolescents with PCOS also had a higher risk of MetS than those with obesity but without PCOS (OR 3.97, 95% CI [1.49, 10.53]). Compared to those without PCOS, systolic blood pressure was higher in adolescents with PCOS (weighted mean difference (WMD) 3.85, 95% CI [1.73, 5.97]), while diastolic blood pressure was higher only in girls with PCOS who had a normal weight (WMD 3.52, 95% CI [1.57, 5.48]). The levels of triglycerides were higher in obese adolescents with PCOS than in those with obesity but without PCOS (WMD 27.84, 95% CI [10.16, 45.51]). PCOS could increase the frequency of MetS by influencing blood pressure and lipid metabolism independent of obesity as early as the adolescent period. Thus, clinicians should perform early interventions in adolescents with PCOS and follow up the relevant indicators of MetS to decrease the risk of poor long-term prognosis.