Although manual-based treatments are widely available in mental health care, they are often not delivered according to protocol. Treatment-, therapist- and organizational-related determinants are known to affect therapist adherence to treatment protocols, and subsequently treatment success. This study examined which determinants are associated with therapist adherence to the Community Reinforcement Approach (CRA) manual, an evidence-based behavioural treatment programme commonly used in addiction care. Using a cross-sectional design, adherence to the CRA manual and potential contributing determinants were assessed through a self-report survey among therapists (N = 69) working in out-patient addiction care. Correlation analysis and backward stepwise regression analysis were used to examine which treatment-, therapist- and organizational-related determinants were associated with CRA adherence. Significant associations with self-reported CRA adherence were found for nine out of 16 determinants examined. Three independent determinants explained 43% of the variance in CRA manual adherence, namely compatibility with the working method therapists were used to, perceived outcome expectations, and perceived adoption of CRA procedures by colleagues. These determinants should be considered when implementing CRA in addiction care, for example by investing in training and taking into account therapists’ previous treatment experience. This also accounts for creating positive outcome expectations and the use of descriptive norms by making experiences explicit of therapists and teams that excel. Future research should investigate which other determinants contribute to therapists’ adherence and focus on clarifying causality between determinants and adherence.

1. (1) To understand the importance of treatment, therapist and organizational determinants influencing therapist adherence to the CRA manual.

2. (2) To explain the three determinants that make the largest contribution to self-reported therapists’ adherence to the CRA manual, namely: compatibility with the working method, perceived outcome expectations, and perceived adoption of CRA procedures by colleagues.

3. (3) To reflect on the clinical implications regarding therapist training, implementation of manual-based treatments and future research.