We examined the mediating effect of self-efficacy on the relationship between personality traits and foreign language anxiety among university students of English as a foreign language. Using a cross-sectional study design, 524 Chinese undergraduate students completed the Foreign Language Classroom Anxiety Scale (FLCAS), the Big Five Inventory (BFI), and the General Self-Efficacy Scale (GSE). The PROCESS mediation analysis findings indicated that personality traits predicted foreign language learning anxiety. Self-efficacy significantly mediated the relationship between personality traits and foreign language anxiety, associated with lower foreign language anxiety. Openness and extroversion were associated with higher self-efficacy and lower foreign language anxiety. Neuroticism was associated with lower self-efficacy and higher foreign language anxiety. Educational programs, therapeutic interventions, and policy measures should be designed to enhance self-efficacy as an asset in foreign language learning experiences.