Objectives: One criticism of the extended parallel process model (EPPM) is its lack of focus on the role of emotion and its relation to behaviour change. Another criticism of the EPPM is regarding its proposition that threat and efficacy have a moderating effect on recipients' attitudes and behaviours. This study aimed to examine emotions and the interaction effects of threat and efficacy to understand their effects on attitudes and behavioural intentions towards colorectal cancer prevention. Methods: The study adopted a pretest-posttest experimental design to collect data from a sample of college students. There were 631 participating students, but the total number of eligible subjects in this study was 402 students. Findings: Analysis shows that (1) anxiety plays a significant role in the reception of fear-appeal messages because it not only directly influences behavioural intentions but is also a full mediator in allowing perceived threat to affect intentions; (2) emotions influence subjects' behavioural intentions but not their attitudes; and (3) perceived threat is more effective in changing subjects' attitudes, while perceived efficacy is more influential in changing behavioural intentions. Conclusion: This study found that it was anxiety rather than fear that made a positive contribution to the effectiveness of fear-appeal messages. These findings showed that the high-threat/high-efficacy group achieved the best persuasive outcomes, followed by the high-threat/low-efficacy and the low-threat/high-efficacy group. The low-threat/low-efficacy group obtained the least persuasive results, which supports the additive model of the EPPM.