This study aimed to investigate the effectiveness of fear appeal messages to promote public engagement with municipal solid waste (MSW) sorting in China using the extended parallel process model (EPPM). By adding information format to the EPPM as guided by the construal-level theory, the study examined whether the interaction effects of threat and efficacy on behavioral intention varied in terms of verbal and numeric information format. The 2 × 2 × 2 factorial experiment revealed a significant main effect for efficacy. The threat, albeit having no significant main effect itself, moderated the effect of efficacy on behavioral intention. Moreover, the significant three-way interaction effect of threat, efficacy, and information format suggested that individuals who received low-threat and high-efficacy messages in numeric format had the highest intention to perform MSW sorting. Findings from this study imply that how messages are presented is of just as much importance as what to communicate to the public when designing environmental campaigns.