Background: Globally, it is estimated that 20% to 40% of all resources spent on health are wasted. Evidence from the African region shows a similar trend wherein limited health sector resources compounded with weak health systems and high disease burden impede effective health service delivery in the continent.The ongoing health sector transformation programme of Ethiopia places considerable interest and focus on improving the performance and efficiency of the health system. Design and Methods: An explanatory sequential mixed methods design was utilized to measure the technical efficiency scores of 94 primary health care facilities and explore the factors that lead to improved performance levels among efficient health care centres. Institutional survey conducted to collect health service input and output data for one fiscal year from July 2018 to 30 June 2019. The Results utilized to pick the best performing health centres. Followed by a qualitative study to explore why and how the high performers standout and identify key drivers of efficiency. Results: The Results showed that out of the ninety-one (91) healthcare centres included in the data envelopment analysis, four (4%) are found to be technically efficient. There is huge variability in efficiency levels of 91 healthcare centres the average tuned at 69 percent. Scale inefficiency was found to be the major source of inefficiency followed by pure technical inefficiency. This study evidenced that at the Addis Ababa level 15% of the healthcare budget can be saved if all healthcare centres achieve the best performance efficiency. The defining features that drive efficiency in three best performing health centres are multifaceted in nature. Conclusions: Technical efficiency measurement sheds light on the possibility of maximising utilisation of limited primary healthcare centre resources. The study highlighted the individual staff, the team, and the institution are fundamentally inseparable components of efficiency drivers.