PurposeAdults who stutter are at risk of developing high levels of social anxiety, leading to negative outcomes and contributing towards stuttering relapse post treatment. To ensure that psychological treatments for social anxiety in stuttering adults are relevant and effective, a broader empirical understanding of the mechanisms of social anxiety in stuttering populations is required. Four key cognitive processing biases identified as maintenance factors in cognitive behavioral models of social anxiety were examined: self-focused attention, safety behavior use, negative self-imagery, and interpretation bias. MethodsAdults who stutter and non-stuttering adults (N = 186) were assessed via an online survey. Participants were categorised into two groups based on stuttering: formally diagnosed stuttering and non-stuttering. Within those groups, participants were further categorised as having low or high levels of social anxiety. Cognitive processing bias was assessed in response to two hypothetical social scenarios (i.e., social interaction and social performance). ResultsAs predicted, in both adults who stutter and who are non-stuttering, high social anxiety was related to greater self-focused attention, safety behavior use and negative self-imagery compared to low social anxiety. No significant effect of social anxiety or stuttering was found in relation to interpretation bias. A significant effect of social anxiety upon negative self-imagery was observed in formally-diagnosed adults who stutter compared to non-stuttering adults. ConclusionThe results support the use of cognitive behavioral models of social anxiety as a framework for research and treatment development within stuttering populations.