Knowledge about parents who seek peer-delivered parent support services in children’s mental health is limited. In this prospective study, characteristics of 124 parents who sought peer parent advocate services related to their children’s behavioral difficulties are described. This urban sample consisted primarily of low-income mothers of color, 80% of whom were caring for children with clinically significant behavioral problems. Of these parents, 64% endorsed clinically significant levels of depressive symptoms at baseline. Linear mixed effects models were used to examine associations between parent depression and anger expression with working alliances with peer advocates. No independent or combined effects of parent depression or anger expression on working alliance were found. However, adjusting for family demographic factors, caregiver strain and child symptoms, parent depression interacted with anger expression to influence working alliances, primarily around agreement and mutual engagement on goals. Among parents who endorsed clinically significant depressive symptoms, anger expression did not influence working alliance but among non-depressed parents, anger expression was negatively associated with working alliance. Implications for training peer parent advocates to more effectively engage low income parents are discussed.