Despite a strong tradition in the literature on the patient information, education and involvement, there are few practical tools available to support hospitals in implementing such strategies. Based on the WHO Health Promoting Hospitals and Health Services (HPH) Strategy, we developed a self-assessment tool for health promotion in hospitals. We describe the development process and validity testing of the tool in a convenience sample of 38 hospitals from eight countries. We computed an overall compliance score, assessed internal consistency and tested associations of self-reported compliance with hospital characteristics, such as accreditation status and being member of the HPH network. The mean compliance with the tool, which assigns a possible score from 0 to 136, was 71.8 (SD 25.0). Floor effects were observed for standards 4 and 5 only (10.5 and 15.8%, respectively), but not for the overall score. Cronbach's alpha for the five scales in the tool ranged from 0.77 to 0.88. Being accredited or being a member of the HPH network was significantly associated with higher overall compliance (score 86.9 versus 64.2, p = 0.012 and 79.3 versus 51.9, p = 0.003, respectively). We developed and established preliminary validity of a self-assessment tool for health promotion in hospitals. Based on assessment of basic psychometric properties, analysis of reliability and construct validity, the tool suggests robustness for self-assessment purposes; however, further research on its validity is strongly warranted if the tool is to be used for other purposes than self-assessment.