Objective This study examines the validity of the Alliance Negotiation Scale (ANS) in a psychotherapy research program. Analyses were designed to evaluate the relationship between the ANS and psychotherapy process and outcome variables. Method Data were collected in a metropolitan psychotherapy research program. Participants completed 30 sessions of therapy, postsession assessments, and a battery of measures at intake and termination. Results Relationships were found between the ANS and session outcome, working alliance, and the presence of ruptures and their resolution. Relationships emerged between the ANS and treatment outcome on measures of psychiatric distress and interpersonal problems. Conclusions The ANS demonstrated relationships with several psychotherapy process and outcome variables. The ANS was the most differentiated from the working alliance on measures of interpersonal functioning and in discriminating personality disorder pathology. These results extend previous findings on the ANS’ psychometric integrity, and offer new data on the relationship between negotiation and treatment outcome.