ObjectiveHospitals are frequently associated with poor working conditions that can lead to work stress and increase the risk for reduced employee well-being. Managers can shape and improve working conditions and thereby, the health of their teams. Thus, as a prerequisite, managers need to be aware of their employees’ stress levels. This study had two objectives: At first, it aimed to test the criterion validity of the Effort-Reward Imbalance (ERI) questionnaire measuring psychosocial workload in hospital employees. Secondly, mean scales of the ERI questionnaire filled in by employees were compared with mean scales of an adapted ERI questionnaire, in which managers assessed working conditions of their employees.MethodsManagers (n = 141) from three hospitals located in Germany assessed working conditions of their employees with an adapted external, other-oriented questionnaire. Employees (n = 197) of the mentioned hospitals completed the short version of the ERI questionnaire to assess their working conditions. Confirmatory factor analyses (CFA) were applied to test factorial validity, using the ERI scales for the two study groups. Criterion validity was assessed with multiple linear regression analysis of associations between ERI scales and well-being among employees.ResultsThe questionnaires demonstrated acceptable psychometric properties in terms of internal consistency of scales, although some indices of model fit resulting from CFA were of borderline significance. Concerning the first objective, effort, reward, and the ratio of effort-reward imbalance were significantly associated with well-being of employees. With regard to the second objective, first tentative findings showed that managers’ ratings of their employees’ effort at work was quite accurate, whereas their reward was overestimated.ConclusionsWith its documented criterion validity the ERI questionnaire can be used as a screening tool of workload among hospital employees. Moreover, in the context of work-related health promotion, managers’ perceptions of their employees’ workload deserve increased attention as first findings point to some discrepancies between their perceptions and those provided by employees.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12995-023-00376-4.