Background The Global Mental Health Assessment Tool — Primary Care Version (GMHAT/PC) has been developed to assist health professionals to make a quick and comprehensive standardised mental health assessment. It has proved to be a reliable and valid tool in a previous study involving GPs. Its use by other health professionals may help in detecting and managing mental disorders in primary care and general health settings. Aim To assess the feasibility of using a computer-assisted diagnostic interview by nurses and to examine the level of agreement between the GMHAT/PC diagnosis and psychiatrists9 clinical diagnosis. Design of study Cross-sectional validation study. Setting Primary care, general healthcare (cardiac rehabilitation clinic), and community mental healthcare settings. Method A total of 215 patients between the ages of 16 and 75 years were assessed by nurses and psychiatrists in various settings: primary care centre (n = 54), cardiac rehabilitation centre (n = 98), and community mental health clinic (n = 63). The time taken for the interview, and feedback from patients and interviewers were indicators of feasibility, and the kappa coefficient (κ), sensitivity, and specificity of the GMHAT/PC diagnosis were measures of validity. Results Mean duration of interview was under 15 minutes. The agreement between nurses9 GMHAT/PC interview-based diagnosis and psychiatrists9 International Classification of Diseases (ICD)–10 criteria-based clinical diagnosis was 80% (κ = 0.76, sensitivity = 0.84, specificity = 0.92). Conclusion The GMHAT/PC can assist nurses to make accurate mental health assessment and diagnosis in various healthcare settings and it is acceptable to patients.