Abstract Background Despite significant reductions in mortality, preventable and treatable conditions remain leading causes of death and illness in children in South Africa. The PACK Child intervention, comprising clinical decision support tool (guide), training strategy and health systems strengthening components, was developed to expand on WHO’s Integrated Management of Childhood Illness programme, extending care of children under 5 years to those aged 0–13 years, those with chronic conditions needing regular follow-up, integration of curative and preventive measures and routine care of the well child. In 2017–2018, PACK Child was piloted in 10 primary healthcare facilities in the Western Cape Province. Here we report findings from an investigation into the contextual features of South African primary care that shaped how clinicians delivered the PACK Child intervention within clinical consultations. Methods Process evaluation using linguistic ethnographic methodology which provides analytical tools for investigating human behaviour, and the shifting meaning of talk and text within context. Methods included semi-structured interviews, focus groups, ethnographic observation, audio-recorded consultations and documentary analysis. Analysis focused on how mapped contextual features structured clinician-caregiver interactions. Results Primary healthcare facilities demonstrated an institutionalised orientation to minimising risk upheld by provincial documentation, providing curative episodic care to children presenting with acute symptoms, and preventive care including immunisations, feeding and growth monitoring, all in children 5 years or younger. Children with chronic illnesses such as asthma rarely receive routine care. These contextual features constrained the ability of clinicians to use the PACK Child guide to facilitate diagnosis of long-term conditions, elicit and manage psychosocial issues, and navigate use of the guide alongside provincial documentation. Conclusion Our findings provide evidence that PACK Child is catalysing a transition to an approach that strikes a balance between assessing and minimising risk on the day of acute presentation and a larger remit of care for children over time. However, optimising success of the intervention requires reviewing priorities for paediatric care which will facilitate enhanced skills, knowledge and deployment of clinical staff to better address acute illnesses and long-term health conditions of children of all ages, as well as complex psychosocial issues surrounding the child.