There is a lack of evidence on the prevalence of smoking among mental health nurses, and the beliefs and attitudes they hold about smoking at work. This paper describes results from a cross-sectional survey of clinical staff working in a UK specialist charitable-status psychiatric hospital and focuses on the responses of registered mental health nurses. Questionnaires specifically developed for this study were sent to all 1371 clinical employees. Completed questionnaires were returned by 167 of 429 (38.9%) registered nurses (RNs), 300 of 842 (35.6%) nursing assistants (NAs), and 123 of 200 (61.5%) other health professionals (OHPs). Twenty-nine (17.4%) RNs, 93 (31%) NAs and eight (6.5%) OHPs reported themselves as current smokers. Differences in response to attitudinal questions between groups could not be attributed to age. RN smokers were significantly more likely than RN non-smokers to state that staff should be allowed to smoke with patients, and to report therapeutic value for patients in this activity. RN smokers were less likely than RN non-smokers to report that patients should be encouraged to stop smoking. RNs were significantly more likely than OHPs to report therapeutic value for patients in smoking with staff, even after controlling for the possible confounding effect of smoking status. Implications of the survey are discussed in the context of the international literature, including the disproportionately high smoking prevalence among patients living in psychiatric institutions and current guidelines to move towards no ‘smoking allowed’ areas for staff working in them.