Parental phubbing can exert negative effects on the adolescents themselves or their interaction with parents. However, less attention has been paid to the interaction with the environment or people outside the family system, such as prosocial behavior. Therefore, this study mainly conducted two studies to explore the influence of parental phubbing on adolescents' prosocial behavior, as well as the mechanisms underlying. Study 1 preliminarily investigated the relationship by using the cross-sectional method (n = 445, Mage = 15.03 ± 0.98 years, 48.3 % were boys). Study 2 adopted a longitudinal study with an interval of 7 months (n = 432, Mage = 14.55 ± 0.61 years, 49.5 % were boys). The participants in two surveys were chosen from Chinese early adolescents. Two studies showed that (1) parental phubbing negatively predicted early adolescents' prosocial behavior; (2) parent-adolescent attachment played a mediating role in the relationship between parental phubbing and early adolescents' prosocial behavior; (3) parent-adolescent attachment and gratitude played sequential mediating roles in the relationship. The results of the present study suggest that parental phubbing deteriorates early adolescents' prosocial behavior through decreasing parent-adolescent attachment, or through parent-adolescent attachment and gratitude together.