ImportanceDespite the availability of several empirically supported trauma-focused interventions, retention in posttraumatic stress disorder (PTSD) psychotherapy is poor. Preliminary efficacy data shows that brief, family-based interventions may improve treatment retention in a veteran’s individual PTSD treatment, although whether this occurs in routine clinical practice is not established.ObjectiveTo characterize receipt of family therapy among veterans diagnosed with PTSD and evaluate whether participation in family therapy is associated with an increased likelihood of completing individual trauma-focused treatment.Design, Setting, and ParticipantsThis retrospective cohort study used the Veterans Health Administration (VHA) Informatics and Computing Infrastructure to extract electronic health record data of participants. All participants were US veterans diagnosed with PTSD between October 1, 2015, and December 31, 2019, who attended at least 1 individual trauma-focused treatment session. Statistical analysis was performed from May to August 2023.ExposuresReceipt of any family psychotherapy and subtype of family-based psychotherapy.Main Outcomes and MeasuresMinimally adequate individual trauma-focused treatment completion (ie, 8 or more sessions of trauma-focused treatment in a 6-month period).ResultsAmong a total of 1 516 887 US veterans with VHA patient data included in the study, 58 653 (3.9%) received any family therapy; 334 645 (23.5%) were Black, 1 006 168 (70.5%) were White, and 86 176 (6.0%) were other race; 1 322 592 (87.2%) were male; 1 201 902 (79.9%) lived in urban areas; and the mean (SD) age at first individual psychotherapy appointment was 52.7 (15.9) years. Among the 58 653 veterans (3.9%) who received any family therapy, 36 913 (62.9%) received undefined family therapy only, 15 528 (26.5%) received trauma-informed cognitive-behavioral conjoint therapy (CBCT) only, 5210 (8.9%) received integrative behavioral couples therapy (IBCT) only, and 282 (0.5%) received behavioral family therapy (BFT) only. Compared with receiving no family therapy, the odds of completing individual PTSD treatment were 7% higher for veterans who also received CBCT (OR, 1.07 [95% CI, 1.01-1.13]) and 68% higher for veterans received undefined family therapy (OR, 1.68 [95% CI, 1.63-1.74]). However, compared with receiving no family therapy care, veterans had 26% lower odds of completing individual PTSD treatment if they were also receiving IBCT (OR, 0.74 [95% CI, 0.66-0.82]).Conclusions and RelevanceIn this cohort study of US veterans, family-based psychotherapies were found to differ substantially in their associations with individual PTSD psychotherapy retention. These findings highlight potential benefits of concurrently providing family-based therapy with individual PTSD treatment but also the need for careful clinical attention to the balance between family-based therapies and individual PTSD treatment.