siblings serve as frequent interaction partners, and their positive exchanges—such as emotional support, affect regulation, and conflict resolution—are often internalized as relational schemas and generalized to other relationships (Brody, 1998). However, prior studies have not directly examined whether warm sibling experiences influence the development of empathy. We propose that such experiences of sibling warmth form positive mental representations that can be temporarily activated, thereby shaping adolescents' emotional and social responses in the moment. Accordingly, the present study investigates whether priming a sibling warmth mindset can enhance adolescents' self-worth and, in turn, increase their empathy. Guided by relational schema theory, we tested the hypothesis that self-worth would mediate the effect of sibling warmth mindset on adolescents' empathic responses. Participants were randomly assigned to either a sibling warmth mindset priming condition (in which they recalled warm interactions with their siblings to activate mental representations of sibling relationships) or a neutral control condition, and then their levels of self-worth and empathy were assessed. Results indicated that priming sibling warmth significantly enhanced adolescents' feelings of self-worth and increased their emotional resonance with others. The mediation analysis further revealed that self-worth played a mediating role in the relationship between sibling warmth mindset priming and empathy. These findings highlight the sibling relationship as a practical tool for promoting adolescent well-being. Parents can be encouraged to nurture positive sibling bonds, knowing they build self-worth and empathy. Schools and social-emotional programs could incorporate brief reflection exercises on sibling support to prime a prosocial mindset and improve peer relationships. Therapists might also activate these positive relational schemas to help clients with low self-esteem. Ultimately, this research positions warm sibling interactions as a potent, yet often overlooked, asset that can be deliberately engaged to foster healthier emotional and social development.