New Zealand (NZ) has low immunisation coverage for infants and children compared to many other westernised countries. Barriers to improving uptake are multifactorial, with health professional knowledge and attitudes identified as important modifiable factors. In NZ practice nurses give most childhood vaccinations in the primary health care setting. This study explored aspects of 150 family practice nurse views, knowledge and experience about immunisation. Qualitative and quantitative text data were obtained through randomised computer assisted telephone surveys and converged using a triangulated multi-method approach. Response rate was 89.3% nurses identified parents' fear as the greatest barrier to achieving better immunisation uptake and disagreed that health professional knowledge was a barrier. However, findings showed lack of knowledge among many participants, despite many feeling confident about their knowledge base. Factors associated with lower practice coverage of infants under 2 years were poorer knowledge of contraindications to vaccination and lack of completion of vaccinator training, especially an update course. A high level of confidence, more years in practice, dedicated time to follow-ups were not associated with better coverage rates. Practice nurses may be unaware that their knowledge in some areas needs improving. A trained practice nurse appears to play a significant role in overcoming fears and maintaining high coverage rates in their practice. We conclude that strategies that focus on primary health care provider support and education are more likely to gain high coverage than those that are purely directed at overcoming access barriers.