Despite numerous studies documenting the high prevalence of social anxiety in children and adolescents with High Functioning Autism Spectrum Disorder (HFASD), there has been little empirical investigation into methods for the assessment of social anxiety in this population. The purpose of this study was to create an empirically derived screening instrument to measure subjective feelings of social anxiety in adolescents and adults with HFASD. Based on a thorough review of the literature in this area, items from all measures (k = 15) used to assess social anxiety in adolescents and adults with HFASD were compiled. After collapsing similar items into one composite item, a pool of 86 items were included in an electronic survey that was sent to experts (n = 99) in the field of anxiety disorders in ASD. Experts ranked the degree to which each item was indicative of social anxiety in HFASD. Based on expert responses, 30 items were selected as the most representative for assessing social anxiety in the target population. In the second phase of the study, experts were asked to rate the final pool of items comprised of the 30 derived from phase I and 10 additional items developed from expert feedback and coding of taped diagnostic interviews with adolescents with HFASD and social anxiety. A final screening measure was derived comprised of 31 items. Future directions and use of the newly formed measure are discussed.