Many studies have found that absenteeism undermines the effective delivery of healthcare. However, most studies focus on high-income countries and low-income countries – which suffer from a shortage of health workers – have been largely ignored in the literature. This study explores absenteeism in primary health centres (PHCs) in Enugu State, Nigeria – a level of the health system identified as susceptible to absenteeism. Ten PHCs were purposively selected from six local governments in Enugu State. In-depth interviews and focus group discussions were conducted with frontline health workers, managers, service users and health facility committee chairpersons. Absenteeism was found to be highly prevalent among health workers, and represents an even bigger burden within PHCs when lateness is also considered. The impact of absenteeism is felt by both service users and co-workers, but it is not always deliberate. Economic pressures, ill-health, challenges regarding transportation and other structural inefficiencies, and managerial/organisational dynamics contribute to the absence of health workers. Although measures exist that aim to reduce absenteeism in PHCs, our findings show that these can be easily circumvented and are ineffective due to implementation and structural issues. The Anti-Corruption Evidence (ACE) approach could be useful here, which seeks to involve and change the incentives of influential stakeholders in the system such that they support efficiency-enhancing policies and ultimately provide effective service delivery. By engaging stakeholders and boundary partners at the grassroots and the level of service delivery, efforts can be made to change behaviours and radically reduce absenteeism at the PHC level.