ImportanceClinician burnout has been associated with clinician outcomes, but the association with patient outcomes remains unclear.ObjectiveTo evaluate the association between clinician burnout and the outcomes of patients receiving of guideline-recommended trauma-focused psychotherapies for posttraumatic stress disorder (PTSD).Design, Setting, and ParticipantsThis cohort study was set at the US Veterans Affairs Health Care System and included licensed therapists who provided trauma-focused psychotherapies and responded to an online survey between May 2 and October 8, 2019, and their patients who initiated a trauma-focused therapy during the following year. Patient data were collected through December 31, 2020. Data were analyzed from May to September 2023.ExposuresTherapists completing the survey reported burnout with a 5-point validated measure taken from the Physician Worklife Study. Burnout was defined as scores of 3 or more.Main Outcomes and MeasuresThe primary outcome was patients’ clinically meaningful improvement in PTSD symptoms according to the PTSD Checklist for the Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition). Patient dropout, therapist adherence, and session spacing was assessed through electronic health records. Multivariable random-effects logistic regression examined the association of therapist burnout and clinically meaningful improvement, adjusted for case-mix.ResultsIn this study, 165 of 180 (91.7%) therapists (89 [53.9%] female) completed the burnout measure and provided trauma-focused psychotherapies to 1268 patients (961 [75.8%] male) with outcome data. Fifty-eight (35.2%) therapists endorsed burnout. One third of patients (431 [34.0%]) met criterion for clinically meaningful improvement. Clinically meaningful improvement in PTSD symptoms was experienced by 120 (28.3%) of the 424 patients seen by therapists who reported burnout and 311 (36.8%) of the 844 patients seen by therapists without burnout. Burnout was associated with lower odds of clinically meaningful improvement (adjusted odds ratio [OR],0.63; 95% CI, 0.48-0.85). The odds of clinically meaningful improvement were reduced for patients who dropped out (OR, 0.15; 95% CI, 0.11-0.20) and had greater session spacing (OR, 0.80; 95% CI, 0.70-0.92). Therapist adherence was not associated with therapy effectiveness. Adjusting for dropout or session spacing did not meaningfully alter the magnitude of the association between burnout and clinically meaningful improvement.Conclusions and RelevanceIn this prospective cohort study, therapist burnout was associated with reduced effectiveness of trauma-focused psychotherapies. Studying when and how burnout affects patient outcomes may inform workplace interventions.