Introduction Primary care is under pressure to achieve accessible, equitable, quality health care, while being increasingly under resourced. There is a need to understand factors that influence quality improvement (QI) to support a high-performing primary care system. Literature highlights the impact of context on QI but there is little primary care research on this topic. Aim This qualitative case study research seeks to discover the contextual factors influencing QI in primary care, and how the relationships between contextual factors, the QI initiative, and the implementation process influence outcomes. Methods The Consolidated Framework for Implementation Research was used to frame this qualitative study exploring primary care experiences in depth. Six sites were selected to provide a sample of rural, urban and Kaupapa Māori settings. Qualitative data was collected via semi-structured interviews and compared and contrasted with the organisational documents and data provided by participants. Results Cases reported success in achieving improved outcomes for patients, practices, and staff. Strong internal cultures of ‘Clan’ and ‘Adhocracy’ typologies supported teamwork, distributed leadership, and a learning climate to facilitate iterative sensemaking activities. To varying degrees, external network relationships provided resources, knowledge, and support. Discussion Organisations were motivated by a combination of patient/community need and organisational culture. Network relationships assisted to varying degrees depending on need. Engaged and distributed leadership based on teamwork was observed, where leadership was shared and emerged at different levels and times as the need arose. A learning climate was supported to enable iterative sensemaking activities to achieve success.