Purpose: Adopting lean principles can unleash several opportunities for firms seeking to increase the efficiency and effectiveness of their product development (PD) process. This study aims to investigate the implementation paths of lean tools in the innovation process of small and medium-sized enterprises (SMEs). Design/methodology/approach: A set of 47 lean tools are identified from the literature and ascribed to the five lean thinking principles, i.e. Value, Map, Flow, Pull and Perfection. Their practical adoption – in terms of “when” and “how” – is then explored in a multiple case study of three SMEs in the manufacturing industry. Findings: SMEs adopt multiple lean tools in different phases of their innovation process. They are still at the beginning of the holistic adoption of lean PD, but some core lean tools, such as A3 reports and visual management, are adopted systematically. Results reveal that specific sets of lean tools and supporting principles are more valuable in certain phases of SMEs innovation process. Specifically, the lean tools concerning the principle of Value and Map can enable the phases of Innovation inputs, Concept development and Solution implementation; the ones ascribed to Flow and Pull the phases of Concept development, Testing and experimentation, and Solution implementation; the Perfection tools to the final phases of Testing and experimentation, Solution implementation and Market introduction. Practical implications: Results provide a reference for SMEs already adopting lean tools in their production process to be extended to the PD process, especially when the delivery of new products is pivotal. Innovative SMEs could evaluate the introduction of specific lean tools in one or more definite phases of their PD process. Originality/value: The study contributes to the literature on the complementarity between lean and innovation by studying the context of SMEs with a process perspective, thus unveiling the potential paths of a widespread application of lean innovation in SMEs.
