Involving organizational members in the planning and implementation of change processes is essential for creating the momentum for lasting change. Therefore, participatory group interventions are a fundamental pillar of organization development. Yet, we know little about the behavioural dynamics that characterize successful group interventions. To address this shortcoming, we analysed 787 minutes (N = 5507 coded statements) of real-time recordings between change agents and recipients. Using lag sequential analysis, we tested which verbal behaviours by change agents elicited recipients’ change readiness, operationalized as their verbatim responses. Furthermore, we explored emerging motivational contagion processes among recipients themselves. Data were collected from two independent samples. Participants took part in a workshop either aimed to reduce their tendency to procrastinate (Study 1) or to enhance their energy-saving behaviour (Study 2). The change agent’s solution-focused as opposed to problem-focused communication stimulated change readiness in both studies. Moreover, recipients’ change statements triggered subsequent change statements by other recipients, providing initial evidence for motivational contagion processes in groups. Finally, compared to a lecture-based intervention, only the energy-saving workshop led to a significant increase in the target behaviour one month after the intervention. Recipients’ change readiness at the end of the workshop was linked to this increase.