This study was conducted with two goals in mind: (1) to explore the mediating roles of L2 enjoyment as a positive emotion and L2 anxiety as a negative emotion in the relationship between Informal Digital Learning of English (IDLE) and L2 willingness to communicate (L2 WTC) in an exam-oriented EFL context, and (2) to further examine whether gender and educational stage play any role in these relationships. Participants include 1,265 Korean EFL learners (764 secondary and 501 tertiary students; 400 males and 865 females). Moderated mediation structural equation modelling results found: (1) L2 enjoyment and L2 anxiety partially mediated the relationship between IDLE and L2 WTC. L2 enjoyment was a stronger mediator than L2 anxiety; (2) IDLE affected females more than males in terms of reducing their L2 anxiety; (3) L2 emotions played a similar mediation role for secondary and tertiary students. These findings advance our understanding of how emotions mediate the association between IDLE and L2 WTC in relation to individual and contextual differences.