Advancements in AI social chatbots’ emotional intelligence offer new avenues for deep emotional engagement, reshaping digital companionship. This study surveyed 1,381 participants to investigate how the roles ascribed to AI social chatbots, alongside users’ emotional involvement, shape emotional self-efficacy through the mediation of self-disclosure depth. It also explores how perceived offline social support moderates such relationships, illustrating the interplay between digital and traditional support systems in fostering self-disclosure. The findings indicate that although most participants reported a heightened emotional involvement during their interactions, these chatbots were predominantly perceived as either friends or mentors rather than partners and family members. More importantly, our analysis shows that emotional involvement significantly increases self-disclosure depth, especially among participants with high perceived social support, ultimately fostering emotional regulation capabilities. This research conceptualizes AI social chatbots as relational entities, applying Media Equation Theory to emotional human-AI communication. Practically, the insights derived from this study offer valuable guidance for technology developers in creating emotionally responsive AI systems that enhance engagement and promote the development of users’ emotional self-efficacy.