The Self-Regulatory Executive Function (S-REF) model of affective dysfunction (Wells & Matthews, 1994) suggests that metacognitive beliefs are important for initiating and maintaining repetitive thought processes in emotional disorders. Rumination is reported by socially anxious individuals, yet it is not known whether this group endorse positive beliefs about the utility of rumination. We predicted that higher levels of social anxiety would be positively associated with stronger positive metacognitive beliefs about rumination. In Study 1 (N = 250 undergraduates), a measure of social anxiety was positively correlated with a measure of positive metacognitive beliefs about rumination, even when controlling for gender and level of depression. Given this result, we then attempted to replicate the finding in another sample, as well as test whether positive metacognitive beliefs about rumination would mediate the relationship between social anxiety and trait rumination. In Study 2 (N = 124 undergraduates), a social anxiety composite measure was positively correlated with a measure of positive metacognitive beliefs about rumination, even when controlling for gender, level of depression and level of rumination. Positive metacognitive beliefs about rumination were also shown to partially mediate the relationship between social anxiety and trait rumination. These results support the S-REF model and provide a potential account of why socially anxious individuals engage in rumination. Implications for the treatment of social anxiety are discussed.