Several reports have recently highlighted the close association between anxiety disorders and bipolar disorder. These reports have indicated a worse course for patients with such comorbidity, including more severe symptoms and poorer outcomes. Fewer studies, however, have closely looked at how social anxiety in particular impacts the clinical presentation and treatment-seeking behavior of people with bipolar disorder. The present report addresses this question using data from the Methods to Improve Diagnostic Assessment and Services (MIDAS) project, one of the largest ongoing clinical epidemiology studies in the United States with over 2,500 participants enrolled to date. Participants were outpatients seeking psychiatric treatment, all of whom underwent an extensive assessment via semi-structured interviews by highly trained diagnosticians. Patients with bipolar disorder and social anxiety (n = 85) were compared to patients with bipolar disorder alone (n = 150) on a series of clinical characteristics, including comorbidity, to determine how social anxiety impacts the clinical presentation of bipolar disorder. Results indicate that comorbid social anxiety is associated with a more severe clinical presentation. Follow-up analyses explored the extent to which this was due to social anxiety specifically versus comorbidity in general. Discussion focuses on how differences in presentation due to comorbid social anxiety and bipolar disorder are likely to impact treatment.