Background: Recent research has indicated that individuals with social interaction anxiety make biased interpretations of positive social interactions, with greater general apprehension in response to such events and more negative predictions about the future. There has also been some preliminary evidence for a second facet of interpretation bias, namely a failure to accept others’ positive reactions at face value, but this has so far not been adequately studied. Method: The present study developed a new measure of this “discounting” dimension and utilized a nonclinical sample of undergraduate students to provide an initial analysis of the scale. Results: Results provide early support for the psychometric properties of our scale, and indicate that discounting mediates the relationship between social interaction anxiety and low positive affect, over and above the previously studied aspect of positive event interpretation bias. Conclusions: The implications for treatment interventions and further research are discussed.