Identifying critical success factors (CSFs) of continuous improvement projects is crucial for management control and operations management domains. Despite the availability of manufacturing-related literature, studies on CSFs in more dynamic and complex healthcare-related operations are scarce. This study, based at a large public tertiary healthcare organization, identifies CSFs in implementing Lean Six Sigma (LSS). 62 LSS projects completed by Green Belts in consultation with Black Belts were analyzed for project success by a review team of practitioners (Black Belters) and academics. Using a grounded theory approach, numerous success factors were initially identified. A series of brainstorming sessions and workshops helped to narrow down and revise all the CSFs present in each of the 62 LSS projects to eight CSFs. The success of the 62 completed projects was assessed against each of the eight CSFs on a five-point Likert scale. Success was measured against whether the project met its stated aim and achieved the Key Performance Indicators that had initially been identified. Finally, the correlations of each factor rating against project success were analyzed to validate the relationship between each success factor and project success. The findings confirm that all eight CSFs identified are significantly correlated to project success. This study contributes to the management control, operations management, and healthcare literature by identifying CSFs of continuous improvement projects and introducing a relatively unique, rigorous, and practically proven evaluation method applied via an industry and academic partnership. Specified CSFs and the method used to identify these will benefit managers of continuous improvement projects.