ABSTRACT Comprehensive sex education (CSE) is linked to several favorable health outcomes yet is consistently underfunded and under-implemented. This is likely due to the perceived controversy of CSE, but research indicates that CSE in the K-12 system is widely supported in most areas of the U.S. Legislators, school board members, and funding agencies need a more thorough and accurate understanding of their communities’ attitudes toward CSE. An attitudinal scale for the general adult population could help generate research that would give these stakeholders the confidence they need to make decisions about CSE in their local areas. The current study created this needed scale using a structured 6-step process that integrated several methods establishing validity and reliability. Scale structure was tested using both exploratory and confirmatory factor analyses, in addition to invariance testing and validity checks. The scale performed similarly across several groups and met predictions for known-groups and predictive validity, while showing some evidence for convergent validity as well. However, although findings indicate that the one-factor model of the CSEA-K12 was the best fitting model, the fit was weaker than desired. Suggestions for future work further addressing internal consistency of the scale are noted.