People living with serious mental illness are often poor and financially vulnerable, but little is known about their experiences of using financial services. Using data from qualitative interviews with 31 clients of a public mental health center, this article explores the use of financial services, including bank accounts, prepaid cards, bill payment methods, saving, and borrowing, by people who have serious mental illness and are poor. We find that financial services do not work well for them, they are frustrated with the associated fees, they struggle to save money (in part due to a lack of effective savings products), and they experience significant rates of arrears and debt. Understanding the use of financial services by this population has implications for developing mechanisms of support, intervention, and regulatory and policy change that will enable them to be more financially healthy, while maximizing their autonomy.