The relationship between financial and mental health represents one of the most significant connections within the financial domain of behavioral health. This chapter examines the complex, bidirectional relationships where financial difficulties can trigger or exacerbate mental health conditions, while mental health challenges simultaneously impair the financial decision-making and management abilities needed for stability. The chapter explores how financial factors intersect with major mental health conditions including trauma, anxiety, depression, stress, suicide risk, psychotic disorders, bipolar disorder, and neurodivergent conditions such as ADHD. Financial trauma, financial anxiety, and the cognitive impacts of depression create distinct patterns that require specialized understanding and intervention approaches. Throughout the chapter emphasizes that sustainable improvement requires simultaneous attention to both psychological and practical financial dimensions rather than treating these domains in isolation. For helping professionals across disciplines, recognizing these interconnections enables more comprehensive assessment, effective intervention planning, and improved outcomes for individuals navigating the complex relationship between financial circumstances and psychological well-being.