AbstractMachinery of Government restructures—transformations that create or abolish departments or move functions between agencies—often result in the misalignment of cultures and subcultures that impact business operations and customer service levels. An understanding of how subcultures are impacted during restructures is vital as they can reveal diffused microcultural boundaries that reflect highly problematic cultural tensions. This study provides rare ethnographic insights into how Machinery of Government restructures destabilise the delivery of optimal customer service by disrupting Business as Usual operations. Based on 74 interviews and ethnographic methods, the integrationist ‘DNA’ culture, subcultures, and emerging microcultures within Service NSW, a public sector agency in New South Wales (Australia), were examined during and after its merger with the Department of Customer Service. Microcultures were shown to function in a way that preserved Business as Usual activities and responsibilities to secure task independence, highlighting the importance of developing a conceptual framework for the detection and resolution of cultural resistance. Scholars and practitioners may adopt the framework used in this study to determine how, when, and where cultural resistance is likely to emerge.Points for practitioners This study critically analyses the ‘DNA’ culture of a service delivery agency in New South Wales during and after its merger with the Department of Customer Service. Service NSW's ‘DNA’ integrationist culture, the broader subculture of its ‘Support Office’, and various microcultures were detected. Microcultures were shown to preserve Business as Usual activities and secure task independence as reflected in backstage sites of enactment. The degree of intra‐ and interpersonal tensions experienced by Service NSW employees was opaque to senior leaders responsible for the restructure. Leaders and practitioners responsible for mergers should fully understand the changing nature of employee language and behaviour. It is advisable they act on the assumption that employees are experiencing tensions resulting from the organisation's disturbed social reality. Scholars and practitioners may adopt the conceptual framework and this case study's methodological approach to analyse a public service agency's various cultures, before, during, and after Machinery of Government (MoG) mergers or restructures, to pre‐empt, identify, and reduce cultural tensions, and should consider the feasibility of appointing a Workplace Change Committee. Workplace Change Committee Members act like first responders across impacted departments and divisions within subcultures. Workplace Change Committee Members manage emerging issues, specifically cultural disparities to ensure both the intra‐ and interpersonal safety of employees impacted by MoG mergers.