This paper presents a comprehensive meta-analysis of fear appeals, examining their effectiveness in influencing attitudes, intentions, and behaviors. The study included 127 papers (9% unpublished) with 248 independent samples (NTotal = 27,372) from diverse populations. The results show a positive effect of fear appeals, with an average effect size of d̅ = 0.29 on a composite index. Moderation analyses based on prominent fear appeal theories revealed that fear appeals were more effective when they included efficacy statements, depicted high susceptibility and severity, recommended one-time behaviors, and targeted audiences with a higher percentage of female recipients. Overall, the study concludes that fear appeals are effective in positively influencing attitudes, intentions, and behaviors, with few circumstances under which they are ineffective or backfire.This paper presents a comprehensive meta-analysis of fear appeals, examining their effectiveness in influencing attitudes, intentions, and behaviors. The study included 127 papers (9% unpublished) with 248 independent samples (NTotal = 27,372) from diverse populations. The results show a positive effect of fear appeals, with an average effect size of d̅ = 0.29 on a composite index. Moderation analyses based on prominent fear appeal theories revealed that fear appeals were more effective when they included efficacy statements, depicted high susceptibility and severity, recommended one-time behaviors, and targeted audiences with a higher percentage of female recipients. Overall, the study concludes that fear appeals are effective in positively influencing attitudes, intentions, and behaviors, with few circumstances under which they are ineffective or backfire.