Purpose This paper aims to identify key middle manager trustworthy behaviours that encourage employees' participation in continuous improvement activities in industrial contexts. Design/methodology/approach The list of behaviours has been developed in two different phases. First, the authors conducted two concept mappings with operators and middle managers and, subsequently, the authors combined and integrated both points of view. Second, the authors developed an expert panel with researchers, consultants and experienced practitioners of industrial management for debugging and reducing the results, presenting the final list of behaviours. Findings This work presents 55 different middle manager trustworthy behaviours divided into four different categories: human qualities; training and development; technical and managerial competencies; and team building. Research limitations/implications This paper contributes to existing literature about sustainable continuous improvement systems highlighting the role of middle managers and proposes a set of specific middle manager trustworthy behaviours for increasing supervisors' influence on operator participation. Originality/value After extracting the knowledge of different stakeholders, the list of behaviours identified can serve as a useful tool for recruiting, training, evaluating and developing a supervisors' managerial style that enhances operator participation in continuous improvement activities.