ABSTRACTEffective training of mental health professionals is crucial for bridging the gap between research and practice when delivering cognitive behavioural therapy (CBT) and motivational interviewing (MI) within community settings. However, previous research has provided inconclusive evidence regarding the impact of training efforts. The current study aimed to systematically search, review and synthesize the literature on CBT and MI training to assess its effect on practitioner behavioural outcomes. Following prospective registration, a literature search was conducted for studies where mental health practitioners were exposed to training in face‐to‐face CBT or MI, reporting on at least one quantitative practitioner behavioural outcome. A total of 116 studies were eligible for the systematic review, and 20 studies were included in four meta‐analyses. The systematic review highlights the need to establish psychometrically valid outcome measures for practitioner behaviour. Results of the meta‐analyses suggest that training has a greater effect on practitioner behaviour change compared to receiving no training or reading a treatment manual. Training combined with consultation/supervision was found to be more effective than training alone, and no differences were found between face‐to‐face and online training. Results should be interpreted with caution due to methodological limitations in the primary studies, large heterogeneity, and small samples in the meta‐analyses. Future directions are discussed.