There is extensive literature on disruptive behavior and on anxiety and a growing literature on co-morbidity. But there is little literature on co-morbidity between disruptive behavior and anxiety, and we found none that specifically discusses social phobia. Because internalizing problems are more difficult to detect than externalizing problems, the latter may obscure the former when they occur together, especially with subtle internalizing problems such as social phobia. We present a case involving co-morbidity between disruptive behavior and social phobia in a 14-year-old boy in residential care. Treatment for social phobia, involving modified public interactions, social-skills training, exposure and reinforcement-based feedback, reduced a high rate of disruptive behavior to near-zero rates.