Background: Digital health literacy (DHL) is becoming increasingly important as a resource for health-related decisions and actions in the context of an ever-increasing density of information in the digital space. Schools are an appropriate setting for promoting DHL, which explicitly includes the DHL of school staff. This article aims to develop and implement an online-based self-assessment tool for the DHL of school staff. Methods: The development of indicators was based on data analyses from a study of 1181 teachers and a complementary literature review of relevant instruments. The development of an evaluation strategy was followed by the technical implementation, piloting, and finalization of the instrument. Results: The instrument comprises 20 indicators on three subject areas: (1) individual DHL, (2) attitudes and competence assessment for teaching DHL, and (3) media competence. The results are prioritized according to the need for action for both the overarching subject areas and the individual indicators. Discussion and conclusion: This instrument offers a low-threshold option for self-assessment of the individual DHL of school staff in Germany, which enables the first step in the development of interventions. The data obtained also help to close the knowledge gap in the DHL of school staff.