PurposeThis study explored how gendered nicknames influence individuals’ prosocial behavior in online interactions and examined the chain mediating roles of warmth and social attractiveness.Participants and methodsAn imaginative context paradigm was used to conduct two experiments in which the participants had to rate their willingness to help users with masculine or feminine nicknames. Experiment 2 further introduced warmth, competence, and interpersonal attraction (social and task) as mediators to test a chain mediation model.ResultsThe participants showed a statistically significant greater willingness to engage in prosocial behavior toward users with feminine nicknames. The mediation analysis revealed that warmth and social attractiveness fully mediated the relationship between gendered nicknames and online prosocial behavior, whereas competence and task attractiveness were non-significant.ConclusionIn the online environment, gendered nicknames shape helping tendencies by influencing cognitive and emotional evaluations. Feminine nicknames evoke warmth and friendliness, enhancing social attractiveness and promoting prosocial intentions. These findings support Eisenberg’s theory of prosocial behavior and highlight how gender stereotypes subtly affect social interactions online.