Co-creation studies have focused on customer-provider value creation in service system. However, the current literature does not consider service co-creation in a multi-actor environment in which behavioural dynamic of individuals plays a role. We propose a model of service co-creation behaviour (SCB) that represents why actors' collaborate in service co-creation. We found seven themes including Platform Capabilities, Relational Capital and Actor Competencies as the key environmental stimuli, and which influence the two actor value perceptions of Purposive value and Network value, which all combine to lead actors to collaborative and citizenship behaviours. The findings provide important implications to theory by extending the co-creation behaviour to actor-to-actor service co-creation context. Practitioners can apply the insights regarding actors' SCB to improve collaborations, hinder destructive behaviours and enrich creative forces to increase value formation.