Background: In China, there are approximately 70 million children, nearly 25% of the child population, who are left behind in the care of other family members when their parents migrate to urban areas, for increased economic opportunities. This paper presents a systematic review and a meta-analysis of studies that have examined the phenomenon of depression among these left-behind children (LBC). Methods: Six hundred three papers published between 2000 and 2017 were retrieved from five databases (China National Knowledge Infrastructure, Wanfang, Weipu, PubMed, and Web of Science).Results: Twenty-one studies (18 in Chinese and 3 in English) met the criteria for inclusion in this meta-analysis. The pooled estimate of depression among LBC was 26.4%. A significant heterogeneity has been found in reported findings, and this heterogeneity was associated with three types of study characteristics, including using an unclear definition of LBC and using invalidated depression instruments, and the geographic location.Conclusions: The risk of mental health problems among this large number of LBC suggests the need to quantify the extent and distribution of their mental health state.Implications for methodological improvements for future research have been discussed.