<p>Health information avoidance (HIA) impedes the adoption of health-promoting behaviors and may result in adverse outcomes due to reliance on incomplete or inaccurate information. While emotion is recognized as a key predictor of HIA, the mechanisms linking negative emotion to HIA remain contested. Based on the motivation dimension of emotion, this study examined the effect of negative emotion (fear and anger) on HIA and explored the mediating role of motivation. Study 1 (<i>N</i> = 254) explored the relationship between negative emotion and HIA. Study 2 employed an experimental-causal-chain design, with Study 2a (<i>N</i> = 245) mapping emotion-motivation linkages and Study 2b (<i>N</i> = 217) testing motivation-HIA pathways. Study 3 expanded this framework. Study 3a (<i>N</i> = 255) validated the full mediation model, while Study 3b (<i>N</i> = 302) demonstrated the robustness of motivation’s mediating role across trait-level individual differences. The results showed that negative emotion, particularly fear, affect HIA via the motivation dimension of emotion. Specifically, negative emotion characterized by higher avoidance motivation was more likely to trigger HIA, independent of individual differences in trait-related variables. This study provides empirical evidence for the mechanism underlying the effect of negative emotion on HIA, enriches the dimension of emotion theory and has important implications for communication of health information.</p>