Recently, promoting high-quality healthcare services has become one of the most challenging goals for healthcare systems worldwide. Lean Six Sigma (LSS) is one of the most abundantly adopted improvement initiatives within any organization, including the healthcare sector, gave its capacity in enhancing the organisation's competitive capabilities noting that human capital holds one of the most critical components of its success. This research aims to assess the impact of Knowledge Management (KM) practice on the implementation of LSS with a focus on the moderating role of the human capital in LSS. The study relied on both descriptive and inferential approaches to identify the significance of human capital KM utility on adopting the LSS model. Using a purposive non-probability sampling approach, data were collected using a structured self-administered questionnaire from 467 supervisory and authoritarian level employees operating in five governmental hospitals in Amman, Jordan. The results confirm the significant positive association of KM in the implementation of LSS within an organisation. Regression results indicate that 61.9% of the variance of LSS implementation can be explained by human capital KM adoption, which was indicated by the 14.1% increase in the interpretation coefficient (R 2 ) when the Human capital variable was considered in the model. The novel aspect of this study is to highlight the significance of the inclusion of human capital as a moderating role in LSS implementation.