This study used multilevel modeling to examine process and treatment adherence factors as predictors of collateral partner reports of abuse following participation in a cognitive-behavioral group treatment program for partner violent men (N = 107). Therapist working alliance ratings predicted lower levels of physical and psychological abuse at the 6-month follow-up and were the strongest predictors of outcome. Homework compliance partially mediated associations between early alliance ratings and psychological abuse at follow-up. Greater group cohesion during treatment, assessed by client report, also predicted lower physical and psychological abuse at follow-up. The findings support the promotion of a collaborative therapeutic environment to induce change among partner violent men. (PsycINFO Database Record (c) 2010 APA, all rights reserved)