There is accumulating evidence that individual differences in stress reactivity contribute to the risk for stress-related disease. However, the assessment of stress reactivity remains challenging, and there is a relative lack of questionnaires reliably assessing this construct. We here present the Perceived Stress Reactivity Scale (PSRS), a 23-item questionnaire with 5 subscales and 1 overall scale, based on an existing German-language instrument. Perceived stress reactivity and related constructs were assessed in N = 2,040 participants from the United Kingdom, the United States, and Germany. The 5-factor structure of the PSRS was found to be similar in the 3 countries. In the U.S. sample the questionnaire was applied using 2 modes of administration (paper-pencil and computerized), and measures were repeated after 4 weeks. Measurement invariance analyses demonstrated full invariance across mode of administration and partial invariance across gender and countries. Scale scores differed between countries and genders, with women scoring higher on most scales. Overall, reliability analysis suggested good stability of PSRS scores over a 4-week period, and validation analysis showed expected associations with related constructs such as self-efficacy, neuroticism, chronic stress, and perceived stress. Perceived stress reactivity was also associated with depressive symptoms and sleep. These associations were particularly strong when individuals scoring high on perceived stress reactivity were exposed to chronic stress. In sum, our findings suggest that the PSRS is a useful and easy-to-administer instrument to assess perceived stress reactivity. (Contains 3 figures and 5 tables.)