Although key differences have been found in boys' and girls' prosocial behavior toward peers, few studies have systematically examined gender differences in how intrinsic perspective-taking abilities theory of mind (ToM) and emotion understanding (EU) and the extrinsic peer environment relate to prosocial behavior. In this prospective longitudinal study, we studied gender differences in the relations between children's observed prosocial behavior and their ToM, EU, and social preference ratings in 114 children (58 boys and 56 girls). We used conventional ToM and EU tasks at 5 and 7 years of age. Observed prosocial behavior in triadic peer interactions was assessed at both time points. Controlling for gender, age, verbal ability, and earlier prosocial behavior, ToM at 5 years was found to predict prosocial behavior at 7 years. Results also revealed gender-differentiated associations at 7 years, whereby only girls' prosocial behavior was positively associated with EU. Results are discussed in terms of gender-differentiated patterns of socialization. (C) 2016 Elsevier Inc. All rights reserved.