Importance Few studies have examined the effects of individual and organizational characteristics on the use of evidence-based practices in mental health care. Improved understanding of these factors could guide future implementation efforts to ensure effective adoption, implementation, and sustainment of evidence-based practices. Objective To estimate the relative contribution of individual and organizational factors on therapist self-reported use of cognitive-behavioral, family, and psychodynamic therapy techniques within the context of a large-scale effort to increase use of evidence-based practices in an urban public mental health system serving youth and families. Design, Setting, and Participants In this observational, cross-sectional study of 23 organizations, data were collected from March 1 through July 25, 2013. We used purposive sampling to recruit the 29 largest child-serving agencies, which together serve approximately 80% of youth receiving publically funded mental health care. The final sample included 19 agencies with 23 sites, 130 therapists, 36 supervisors, and 22 executive administrators. Main Outcomes and Measures Therapist self-reported use of cognitive-behavioral, family, and psychodynamic therapy techniques, as measured by the Therapist Procedures Checklist–Family Revised. Results Individual factors accounted for the following percentages of the overall variation: cognitive-behavioral therapy techniques, 16%; family therapy techniques, 7%; and psychodynamic therapy techniques, 20%. Organizational factors accounted for the following percentages of the overall variation: cognitive-behavioral therapy techniques, 23%; family therapy techniques, 19%; and psychodynamic therapy techniques, 7%. Older therapists and therapists with more open attitudes were more likely to endorse use of cognitive-behavioral therapy techniques, as were those in organizations that had spent fewer years participating in evidence-based practice initiatives, had more resistant cultures, and had more functional climates. Women were more likely to endorse use of family therapy techniques, as were those in organizations employing more fee-for-service staff and with more stressful climates. Therapists with more divergent attitudes and less knowledge about evidence-based practices were more likely to use psychodynamic therapy techniques. Conclusions and Relevance This study suggests that individual and organizational factors are important in explaining therapist behavior and use of evidence-based practices, but the relative importance varies by therapeutic technique.