Purpose: The increase in cost-sharing between patients and payers has resulted in financial toxicity in cancer patients, particularly among young adult (YA) patients and survivors (<40 years of age). This study explored financial toxicity and its impact on psychological well-being, self-efficacy for coping with cancer, and cost-coping behaviors among a sample of YA cancer patients and survivors. Methods: One hundred forty YAs completed an anonymous online survey. The Comprehensive Score for Financial Toxicity measured financial toxicity and the Cancer Behavior Inventory-Brief measured coping self-efficacy. The Patient Health Questionnaire-4 and items from the Impact of Cancer-Young Adult and the Cancer Needs Questionnaire-Young People assessed psychological well-being. A single item assessed cost-coping behaviors (i.e., skipping or delaying treatment because of its cost). Analyses included Pearson and Spearman correlation matrices and multivariate regression modeling. Results: Worse financial toxicity was associated with lower insurance satisfaction (r = 0.52, p < 0.001), higher levels of depressive and anxiety symptoms (r = -0.42, p < 0.001), greater worry (p < 0.001), and lower self-efficacy in coping with cancer (i.e., maintaining independence and a positive attitude, r = 0.41, p < 0.001; coping and stress management, r = 0.43, p < 0.001; and managing negative effect, r = 0.20, p = 0.02). In multivariate modeling, financial toxicity related to skipping or delaying treatment and greater anxiety and depression symptomology, controlling for relevant covariates. Conclusion: The findings suggest financial toxicity negatively impacts many facets of the YA cancer experience. There is a need to address the cost of cancer care with patients to ensure they are informed about the financial implications of treatment decisions and to support financial planning as needed.