Marginalized youth are at elevated risk for mental health difficulties, yet they encounter numerous barriers to engagement with mental health services. Past negative experiences with family, social workers, and systems of care contribute to distrust of service providers and ambivalence about engaging in trusting relationships with adults. This longitudinal qualitative study explored how marginalized youth living with mental health conditions make decisions about trust in their relationships with helping professionals. Semi-structured, open-ended in-depth interviews were conducted with 13 young women living with a mood or anxiety disorder, exploring trust, mutuality, and disconnection in relationships between marginalized youth and helping professionals. Eleven of the participants also participated in a second interview, 3 months later, that explored participants’ relationships with friends and family. Transcripts were analyzed using thematic analysis and interpreted through the lens of relational-cultural theory. Results indicated that the majority of interview participants described feeling unseen, judged, or invalidated in their relationships with family members. Four themes emerged as factors in the assessment of the trustworthiness of service providers: genuine caring; understanding; non-judgmental acceptance; and adult respect for youth agency. Concerns about confidentiality and mandated reporting informed participants’ decisions about disclosure in these relationships. Analysis of findings reveals evidence of the central relational paradox in these descriptions of helping relationships, reflecting the simultaneous appeal and peril of vulnerability in relationships, especially relationships characterized by power differentials. Findings suggest that practitioners working with marginalized youth can expect both openness and guardedness in the treatment relationship.