In this study, an assessment tool was developed to measure the reasoning skills (RS) of preservice science teachers on socio-scientific issues (SSI). As a result of the literature review, the scale was developed based on five dimensions. These dimensions are complexity, questioning, having different perspectives, skeptical approach and the limitations and adequacy of science. The developed scale consists of a total of 18 items. 577 preservice science teachers participated in the study voluntarily. First-level confirmatory factor analysis (CFA) was conducted to evaluate the construct validity of the items created in line with the theoretical framework. In addition, second-level CFA was applied to test whether the dimensions represented the students' perceptions of socio-scientific reasoning (SSR) skills. When the literature was examined, it was decided that the values of the fit indices were appropriate for model verification. The findings reveal that the developed scale can be used for valid and reliable measurements in determining the perceptions of preservice teachers regarding their SSR skills.