Purpose The purpose of this paper is to explore the extent of Lean Six Sigma (LSS) implementation within manufacturing companies in the West of Ireland. It examines the key success and failure factors, benefits and quality tools influencing LSS projects deployment. Design/methodology/approach The study adopted a mixed research method (quantitative and qualitative approach). Research data were collected through a structured survey questionnaire to the target population followed by interview case studies with four manufacturing companies to gather additional insight. The targeted respondents were manufacturing engineers, quality engineers, process improvement managers, operations managers, R&D engineers, LSS experts and validation engineers. Findings LSS initiatives are still relatively unknown to many SMEs organisations, whereas large companies have adopted LSS for some time. Top management commitment, understanding the LSS methodology, tools and techniques, integrating LSS to business strategy, organisational cultural change and training and education were the topmost key success factors. Organisational strategy, lack of top management support, expensive cost for LSS projects, unclear prioritisation of LSS projects and cost effectiveness were the most important failure factors influencing LSS implementation. Originality/value This research is the original work provided by the author and is expected to address the shortcomings of both SMEs and large organisations in the West of Ireland. The recommendations and frameworks reported in this paper can be used by manufacturing and service companies in Ireland for efficiency, competitiveness and continuous improvement.