Empathy is a key socio-emotional skill in early adolescence, and numerous school-based programs attempt to foster empathy in students. In this field experiment, we took a novel approach to building empathy among early adolescents in four schools (n = 857), rather than addressing the ability to empathize, we targeted the motivation to empathize. We leveraged two strategies previously demonstrated to change empathy-related motivation (social norms and mindsets). Students who received a norms-based intervention, compared to those in other conditions—experienced greater motivation to empathize, which indirectly affected their prosocial behavior as reported by peers. The effects of this norms condition were strongest at schools with relatively high engagement with the intervention. Findings suggest a novel avenue for increasing empathy among adolescents—by focusing on peer-driven motivation—and underscore the importance of context in shaping intervention outcomes.