Objective: To evaluate the neglect of left-behind children (LBC) in China. Method: Participants: Children separated from one or both parents for at least 6 months. Intervention: Trauma of separation. Comparison: Non-left-behind children (NLBC). Outcomes: Neglect rates and severity. Only case–control studies were included. Results: Thirteen studies were included; there were 18,688 LBC in a large sample ( N = 42,003) of children aged 0–18 years in China. The overall neglect rate was significantly higher in LBC compared to NLBC (odds ratio [ OR] = 1.58, 95% confidence interval [CI] = [1.50, 1.67], p < .01) based on the Chinese Rural Child Neglected Evaluation Model (CRCNEM) and the Parents–Child Conflict Tactics Scales ( OR = 1.44, 95% CI [1.35, 1.54], p < .01). The overall neglect severity in LBC was also significantly higher than NLBC ( SMD = 0.31, 95% CI [0.28, 0.33], p < .01). The same trends were observed in sex subgroups. With regard to subtypes, LBC were significantly more likely to have emotional neglect ( OR = 2.29, 95% CI [1.88, 2.78], p < .01), medical neglect ( OR = 1.79, 95% CI [1.62, 1.98], p < .01), physical neglect ( OR = 1.75, 95% CI [1.60, 1.91], p < .01), security neglect ( OR = 1.52, 95% CI [1.32, 1.75], p < .01), educational neglect ( OR = 1.50, 95% CI [1.31, 1.72], p < .01), and social neglect ( OR = 1.33, 95% CI [1.18, 1.51], p < .01). Furthermore, LBC had significantly higher severity in medical neglect ( SMD = 0.31, 95% CI [0.27, 0.35], p < .01), emotional neglect ( SMD = 0.28, 95% CI [0.24, 0.32], p < .01), physical neglect ( SMD = 0.24, 95% CI [0.18, 0.29], p < .01), security neglect ( SMD = 0.26, 95% CI [0.23, 0.29], p < .01), educational neglect ( SMD = 0.25, 95% CI [0.20, 0.31], p < .01), and social neglect ( SMD = 0.25, 95% CI [0.10, 0.40], p < .01). Conclusion: The neglect rates and severity in LBC in China were both significantly higher than those in NLBC. There was a strong association between neglect and LBC. Public policy changes are urgently needed to improve the dire situation and the well-being of the LBC.