Background Social climate has an influence on a number of treatment‐related factors, including service users' behaviour, staff morale and treatment outcomes. Reliable assessment of social climate is, therefore, beneficial within forensic mental health settings. The Essen Climate Evaluation Schema (EssenCES) has been validated in forensic mental health services in the UK and Germany. Preliminary normative data have been produced for UK high‐security national health services and German medium‐security and high‐security services. Aims We aim to validate the use of the EssenCES scale (English version) and provide preliminary normative data in UK medium‐security hospital settings. Methods The EssenCES scale was completed in a medium‐security mental health service as part of a service‐wide audit. A total of 89 patients and 112 staff completed the EssenCES. Results The three‐factor structure of the EssenCES and its internal construct validity were maintained within the sample. Scores from this medium‐security hospital sample were significantly higher than those from earlier high‐security hospital data, with three exceptions – ‘patient cohesion’ according to the patients and ‘therapeutic hold’ according to staff and patients. Conclusion Our data support the use of the EssenCES scale as a valid measure for assessing social climate within medium‐security hospital settings. Significant differences between the means of high‐security and medium‐security service samples imply that degree of security is a relevant factor affecting the ward climate and that in monitoring quality of secure services, it is likely to be important to apply different scores to reflect standards. Copyright © 2013 John Wiley & Sons, Ltd.