Objective: The paper presents the development of a coding tool for self-efficacy orientated interventions in diabetes self-management programmes (Analysis System for Self-Efficacy Training, ASSET) and explores its construct validity and clinical utility. Methods: Based on four sources of self-efficacy (i.e., mastery experience, role modelling, verbal persuasion and physiological and affective states), published self-efficacy based interventions for diabetes care were analysed in order to identify specific verbal behavioural techniques. Video-recorded facilitating behaviours were evaluated using ASSET. Results: The reliability between four coders was high (K = 0.71). ASSET enabled assessment of both self-efficacy based techniques and participants' response to those techniques. Individual patterns of delivery and shifts over time across facilitators were found. In the presented intervention we observed that self-efficacy utterances were followed by longer patient verbal responses than non-self-efficacy utterances. Conclusion: These detailed analyses with ASSET provide rich data and give the researcher an insight into the underlying mechanism of the intervention process. Practice implications: By providing a detailed description of self-efficacy strategies ASSET can be used by health care professionals to guide reflective practice and support training programmes.