To reach the goal of healthy workplaces, psychosocial risks at the workplace (also called “mental stress”) must be assessed and managed for every workplace. Psychosocial risks have to be assessed as widely as possible to support deriving tailored interventions for organizations. The OrgFit was constructed to capture all relevant areas of stress according to international requirements (e.g., according to the ISO 10075-1 or the Framework Directive 89/391/ EEC). In this paper, the psychometric properties of the OrgFit were investigated in two studies. The first study aimed at testing the factorial structure of the OrgFit with an exploratory factor analysis. In the second study, an additional factor analysis was conducted and construct validity between the dimensions of the OrgFit and work-related strain (convergent validity) and recovery/resources (discriminant validity) was tested. In both studies, Austrian workers were invited to participate in an online study by sending out e-mails. With this procedure, representative samples of 514 workers (study I) and 1200 workers (study II) were obtained to conduct the analyses. Factor structure as well as reliability and validity coefficients show satisfactory results. The internal consistencies show values between 0.79 and 0.93, which meets the requirement for analyses on an organizational level. The validity analyses indicate that the dimensions in the OrgFit are capable of assessing stress that might lead to negative strain outcomes. The OrgFit can be used in the process of risk assessment for a comprehensive assessment of mental stress and can serve as a base for developing specific process-and structure-oriented interventions.