Background: The Warwick–Edinburgh Mental Well-being Scale (WEMWBS) is a relatively new measure and to date has been validated in student samples in England and Scotland, and in population samples in Scotland. No data exist on the psychometric properties of the WEMWBS when used within a general population in Northern Ireland, a region that might be expected to differ in health and wellbeing given its troubled history. Aims: This paper represents the first attempt to assess mental well-being in Northern Ireland using this new questionnaire. Method: Data came from the 2009/2010 Continuous Household Survey and analyses are based on the responses of 3355 people aged 16 years and over who completed the full WEMWBS. Results: The results suggest that the data collected using the WEMWBS among a large-scale random sample of adults in Northern Ireland are comparable to those produced for adults in other parts of the UK. Conclusion: The findings from this study are important as any measure of mental well-being purported to have been validated for the UK needs to include Northern Ireland, given that region’s recent history in terms of the civil conflict and its potential impact on the health and well-being of its population.