Social Anxiety Disorder (SAD) is characterized by a tendency to interpret ambiguous social cues as negative. Here we tested whether interpretation of ambiguous faces differs between participants with SAD and non-anxious controls. Twenty-seven individuals with SAD and 21 non-anxious control participants completed an emotion recognition task in which they judged ambiguous morphed faces as happy or angry. Participants with SAD judged a higher proportion of the faces as angry compared to non-anxious participants, and were slower to judge faces as angry compared to happy, while no such reaction time bias manifested in the control group. Finally, happy judgments were slower in the SAD group compared to the control group, while angry judgments were faster in the SAD group compared to the control group. These findings provide evidence for a negative bias in resolving emotional ambiguity in facial expressions among individuals with SAD.