<p>This study validated the Fear of Happiness Scale (FHS) in a South Korean population and examined its psychometric properties, demographic correlates, and incremental validity in predicting depression and anxiety. Two independent community samples were recruited (Sample 1: <i>n</i> = 1300, age = 18–59; Sample 2: <i>n</i> = 1079, age = 19–35). Exploratory and confirmatory factor analyses supported a robust unidimensional structure, with factor loadings ranging from .72 to .85. The FHS demonstrated excellent internal consistency (McDonald’s ω = .90–.91) and strong convergent validity with measures of self-attitudes, alexithymia, emotion dysregulation, depression, and anxiety (all <i>r</i>s = .32–.50). Convergent validity was further supported by high average variance extracted (AVE = .64) and construct reliability (CR = .90). Measurement invariance was established across gender and education levels and was partially supported across age groups. Regression analyses indicated that younger age and lower education were associated with greater fear of happiness, while gender differences were nonsignificant. Hierarchical regression analyses showed that fear of happiness predicted depressive symptoms beyond demographic and psychological variables (Sample 1: ∆<i>R</i>² = .002, <i>p</i> = .016; Sample 2: ∆<i>R</i>² = .016, <i>p</i> &lt; .001), although the effect was small in Sample 1. Its predictive role in anxiety was inconsistent (Sample 1: ∆<i>R</i>² &lt; .001, <i>p</i> = .691; Sample 2: ∆<i>R</i>² = .014, <i>p</i> &lt; .001). Overall, the findings provide strong evidence for the reliability and validity of the FHS in a Korean context and highlight fear of happiness as a potential transdiagnostic cognitive–emotional vulnerability, particularly in relation to depression.</p>