<p>Oxytocin system genes interact with parenting behavior to influence children’s prosocial behaviors. Brain oxytocin levels may have a U-shaped relationship with environmental sensitivity. However, it remains unknown whether oxytocin system genes influence individual environmental sensitivity by affecting brain oxytocin levels, thereby modulating the relationship between the environment (e.g., parental control) and children’s prosocial behaviors. The present study examined this issue in sample of 604 Chinese children (<i>M</i>_<i>age</i> = 9.88 years, <i>SD</i>_<i>age</i> = 0.33; 294 girls, 48.68%). Saliva samples were collected to genotype genes, and children completed questionnaires to assess parental control and prosocial behaviors. Three selected single nucleotide polymorphisms (SNPs) were combined in a multilocus genetic profile score (MGPS) reflecting additive effects on brain oxytocin levels. Results showed significant quadratic interaction effects of oxytocin system’s MGPS and parental behavioral control on children’s prosocial behaviors and its subtype-comforting behavior. Children with either higher or lower MGPS (vs. moderate MGPS) exhibited higher environmental sensitivity, and thus their prosocial behaviors, particularly comforting behavior, was more susceptible to parental behavioral control. The present study provided evidence for the nonlinear relationship between oxytocin system genes and environmental sensitivity and the genetic and environmental mechanisms underlying children’s prosocial behaviors, especially comforting behavior.</p>