PurposeThe purpose of this paper is to present an attempt to develop an instrument containing operational measures of lean combined with safety and ergonomic conditions in a workstation or production line. This operational tool aims to help researchers and practitioners to prioritize and evaluate the lean implementations, as well as the ergonomic and safety conditions, in an integrated way.Design/methodology/approachLean manufacturing methods and principles, as well as safety and ergonomics aspects, were exhaustively researched with the ultimate goal of finding a way to improve the workplace by taking into account the efficiency and well-being of workers. The instrument was validated in an interactive process between theory and practical insights. At the end, it was tested in several workstations/production areas.FindingsThe study reveals that high scores are derived from a good interaction between lean, ergonomics and safety.Research limitations/implicationsIt would be important to validate it in different companies and different types of industries because each one has its own characteristics.Practical implicationsThis tool helps practitioners (technicians and ergonomic practitioners from manufacturing companies) assess the implementation of lean principles and the safety issues in their processes. It also allows managers to evaluate their business and identify the priority areas to improve according to the previously defined company’s aims.Originality/valueAs Peter Drucker said: “If you can’t measure it, you can’t improve it.” For a successful implementation, managers should start the lean journey with a lean assessment and make it in a regular basis. To the authors’ knowledge, there are various lean assessment tools, but this work is innovative because it provides an assessment instrument to evaluate organizations’ workstations/production areas simultaneously in three dimensions: lean, safety and ergonomic aspects.