A reluctance of nonspecialists to work with drug and alcohol misusers have focused upon belief-based systems, including therapeutic commitment (TC) and situation-specific constraints. This paper describes the development and assessment of a theoretical model for nonspecialist drug workers, characterised as a synthesis of attitudinal and constraints explanations. A cohort of 189 nonspecialist drug workers completed self-report measures of overall TC and situational constraints scales. Predictive analysis of associations between TC, role security (RS), role requirements, and situational constraints was performed to explore direct and indirect effects. Such assessment allowed for the identification of a predictive process by which TC may be established, manipulated, and maintained. Levels of TC were found to be explained by the direct effects of self-esteem (SE), situational constraints, role support, and RS. Role support and situational constraints were also found to have indirect effects. Experience with working with drug users and education on drug-related issues were found to have predominantly indirect effects on TC via situational constraints and RS. Findings show the synthesised model to be partially supported. Implications for the development of a process-driven theoretical understanding of TC and situational constraints are discussed, and applied recommendations for training intervention are presented.