Abstract: Based on a survey of 298 junior students from a senior middle school, this study investigates the mediating effect of self-efficacy in the relationship between the tolerance of ambiguity and foreign language learning anxiety. The results show that: (1) tolerance of ambiguity and students’ language learning anxiety are significantly correlated, with the former a strong predictor of the latter; (2) tolerance of ambiguity predicts foreign language learning self-efficacy; (3) target self-efficacy, task-enabling self-efficacy, difficulty-handling self-efficacy play mediating roles between tolerance of ambiguity and foreign language learning anxiety, and thus self-efficacy indirectly influences learning anxiety.