Background: Emotional reactivity is an important construct to consider when studying mental disorders. This study was conducted to translate and assess the factor structure, construct validity and internal consistency of a German version of the Emotion Reactivity Scale (ERS), which is an originally English questionnaire assessing three components of emotional reactivity: sensitivity, intensity and persistence of emotions. Methods: The German ERS and a range of questionnaires used to assess convergent and discriminant validity were completed by 334 German speaking Swiss participants. Results: Confirmatory factor analysis showed strong support for a bi-factor model, with evaluation indices pointing to a unidimensional construct rather than to domain specific factors. The questionnaire showed good reliability and the factor structure was similar across gender. The ERS showed convergent validity with general psychopathology, behavioral inhibition, negative affect, orienting sensitivity, depressive symptoms and symptoms of disordered eating, and discriminant validity with behavioral activation and alcohol consumption. Conclusions: Findings support the construct validity of the German ERS and suggest that it assesses a unidimensional construct with high internal consistency. Accounting for the unidimensional nature of the scale and aiming for efficient assessment tools, future research could, based on these findings, develop and evaluate the psychometric properties of a short version of the ERS.