Perfectionism has traditionally been conceptualised as a personality trait. However, researchers have recently proposed a new construct–perfectionistic climate–which focusses on the degree to which the social environment is experienced as perfectionistic. In the current study, we apply this new construct to sport and begin the development and validation of the first scale to measure perfectionistic climate – the Perfectionistic Climate Questionnaire-Sport (PCQ-S). This self-report scale includes five components of coach behaviour central to perfectionistic climate: expectations, criticism, control, conditional regard, and anxiousness. The development of the PCQ-S included five stages and data from four samples of youth athletes (N = 730 total; Mage = 14.50, s = 1.83). In stage one, outlined in study one, PCQ-S items were generated and then refined using feedback provided by academics, sport coaches, and youth athletes. In stage two, outlined in studies two and three, exploratory factor analysis, confirmatory factor analysis, and exploratory structural equation modelling techniques were used to examine the structure of PCQ-S items. In stage three, outlined in study four, discriminant validity was assessed by estimating the nomological network of relations between test scores on the PCQ-S and established coach climate measures. Then, in the final stage, outlined in study five, measurement invariance of the PCQ-S was examined across gender and age groups. The result of this process was a 20-item five-factor instrument that shows evidence of good factorial validity, can be differentiated from existing coach climate measures, and has measurement invariance. Based on these initial findings, the PCQ-S provides the first valid and reliable way of measuring perfectionistic climate in sport.