A growing body of literature has documented interpersonal factors associated with the occurrence and treatment of posttraumatic stress disorder (PTSD). Among these factors, intimate partners’ psychological functioning has consistently been found to be associated with patients’ PTSD severity. The present study investigated intimate partners’ psychological functioning outcomes in a sample of 40 partners of individuals with PTSD within a randomized waitlist controlled trial of cognitive-behavioural conjoint therapy for PTSD. In addition, models of influence from partners to patients and vice versa were examined. More specifically, these models investigated the influence of pretreatment functioning and symptom change on treatment outcomes. There were no significant differences between active treatment and waitlist in intimate partners’ psychological functioning at posttreatment. Furthermore, neither partners’ psychological functioning, nor patients’ PTSD symptoms, influenced the others’ treatment outcomes. Findings are discussed with a focus on guiding future research on partners’ psychological functioning in the context of PTSD.