The objective of the study reported here is to systematically estimate the prevalence of depressive symptoms among adolescents in secondary schools in mainland China. Literature searches were conducted in both English and Chinese databases from database inception to January 2018. This meta-analysis used a random-effects model to estimate the prevalence of depressive symptoms. Fifty-one eligible studies ( n = 144,060) using probability sampling were identified. The results revealed a pooled prevalence of depressive symptoms of 24.3% (95% CI, 21.3%–27.6%), with high between-studies heterogeneity ( Q = 9909, I² = 99.5%, p < 0.001). The prevalence estimates reported by the individual studies ranged from 6.2% to 64.8%. There was an increased prevalence with increasing grades from year 1 in junior secondary school (24.5%; 95% CI, 17.8%–32.8%) to year 3 in senior secondary school (40.1%; 95% CI, 29.4%–51.9%) ( Q = 7.1, p < 0.01). Potential sources of high heterogeneity of prevalence among studies can be accounted for by screening instruments with different cutoffs. Further analysis stratified by gender, grade, household registration ( hukou ) and number of children in the household were performed. Limitations include the high level of heterogeneity between studies (mainly from the heterogeneity of measurement tools) and stringent inclusion and exclusion criteria. This study suggests that depressive symptoms are common among Chinese secondary school students . Further research is needed to identify the risk factors and effective strategies for preventing and treating depression among adolescents in secondary schools.