Previous studies have found that social anxiety and experiential avoidance (EA) are significantly associated, but the directionality of this relationship has not been firmly established. The present study examined momentary EA and social anxiety using repeated measurements during an opposite-sex interaction. Participants were 164 individuals (50% female): 42 were diagnosed with social anxiety disorder (SAD) and the remaining 122 were non-socially-anxious individuals (NSAs). Participants formed 42 experimental dyads including 1 individual with SAD and 1 NSA individual, and 40 control dyads including 2 NSA individuals. Lower-level mediational modeling indicated that for individuals with SAD, a reciprocal relationship was observed in which changes in both EA and social anxiety mediated changes in each other. However, changes in EA explained approximately 89% of changes in social anxiety whereas changes in social anxiety explained approximately 52% of changes in EA throughout the interaction. For NSA individuals, only social anxiety predicted EA. These findings point to a deleterious cycle driven mostly by EA among individuals with SAD, but not NSA individuals. Findings are discussed within the context of previous empirical findings as well as acceptance and commitment therapy (ACT) and cognitive-behavioral models of psychopathology.