Evidence from population and experimental studies suggests that laypersons’ beliefs about stress influence mental and physical health. Yet, studies so far have solely relied on psychometrically not evaluated instruments to measure stress beliefs. Standardized assessment is needed to facilitate research on this novel and promising construct in stress research. This study reports on the development and psychometric evaluation of a new questionnaire to assess stress beliefs: The Beliefs About Stress Scale (BASS). An item pool of 24 statements on stress beliefs was administered to N = 455 university students at the beginning of term via an online survey. Additionally, participants’ subjective stress levels, optimism, pessimism, neuroticism and somatosensory amplification were assessed. A subsample of N = 216 participants was reassessed during end of term exams 6 to 8 weeks later. Using a split sample procedure, both exploratory and confirmatory factor analysis suggested 3 dimensions of stress beliefs: negative stress beliefs, positive stress beliefs, controllability. The scales showed good to acceptable internal consistency (Cronbach α = .73–.87) and retest-reliability (rtt6-8 = .61–.81). Correlations with optimism, pessimism, neuroticism and somatosensory amplification (r = .15–.47) indicated high to medium discriminant validity. Moreover, baseline negative stress beliefs appeared to be associated with an increased level of stress at end of term exams 6 to 8 weeks later by statistical trend (β = .11; p = .062). Stress beliefs appear to be multidimensional and stable over time. The BASS offers a promising new way to assess stress beliefs via a brief, psychometrically evaluated questionnaire.