Therapist drift refers to the tendency for psychologists to move away from the delivery of the evidence-based practices in which they are trained, even when resourced to implement them. When therapists do not provide, or only partially provide, empirically supported treatments their patients may receive interventions that are not effective, or that are harmful. The aim of the current study was to conduct a systematic review of the literature to ascertain the correlates of therapist drift in psychological practice, focusing on therapist characteristics. Relevant articles were identified through a comprehensive search of the literature. Sixty-six studies met the inclusion criteria and nine therapist characteristics that correlate with therapist drift were identified. These characteristics included: (1) therapist knowledge; (2) attitudes toward research; (3) therapist anxiety; (4) clinical experience; (5) therapist age; (6) theoretical orientation; (7) critical thinking; (8) personality traits; and (9) cultural competency. The interrelationships between these factors are explored and the clinical implications of results are discussed. Recommendations are made for future research.