The purpose of this research was to develop a measure of sport injury anxiety (SIA), defined as the tendency to make threat appraisals in sport situations where injury is seen as possible and/or likely. The Sport Injury Anxiety Scale (SIAS) was developed in three stages. In Stage 1, expert raters evaluated items to determine their adequacy. In Stage 2, 491 collegiate athletes completed the preliminary SIAS. Results of an exploratory factor analysis (EFA) revealed a reliable scale with seven subscales, including anxiety associated with: (a) loss of athleticism, (b) being perceived as weak, (c) experiencing pain, (d) loss of social support, (e) letting down important others, (f) reinjury, and (g) having an impaired self-image. Confirmatory factor analyses (CFAs) supported a shortened scale and the multidimensional and hierarchical structure of SIAS scores. In Stage 3, 284 collegiate athletes completed the 21-item SIAS and other measures. Analyses supported the construct validity of the SIAS.