The purpose of this study was to develop and provide a preliminary validation of a new measure of scrupulosity, the Scrupulous Thoughts and Behaviours Questionnaire (STBQ). More specifically, the STBQ was designed to assess a range of scrupulosity-related thoughts/obsessions and behaviours/compulsions. Following item development, a sample of non-referred college students completed the STBQ along with numerous validation measures. Based on factor analyses, a two-factor solution was retained. The first factor consisted of items that measure scrupulosity-themed obsessions and thoughts, and the second factor consisted of items that measure scrupulosity-themed compulsions and related behaviours. Support was found for the validity of STBQ, as both subscales were significantly and positively associated with measures of relevant constructs, including the Pennsylvania Inventory of Scrupulosity-Revised, the only other self-report measure of scrupulosity, thought–action fusion, religiosity, and obsessive–compulsive disorder symptoms. As the first known self-report measure to assess scrupulosity obsessions and compulsions, the STBQ has a potential utility in clinical practice and research.