To estimate the proportion and correlates of self-reported financial difficulty among patients with multiple myeloma (MM) or chronic lymphocytic leukemia (CLL). 23 U.S. community and minority oncology practice sites affiliated with the National Cancer Institute Community Oncology Research Program (NCORP). 521 patients (≥18 years) with MM or CLL were consented and 416 responded to a survey (completion rate=79.8%). Respondents had a MM diagnosis (74.0%), an associate degree or higher (53.4%), were White (89.2%), insured (100%) and treated with clinician-administered drugs (68.0%). Observational, prospective, protocol-based survey administered in 2019-2020. Financial difficulty was assessed using a single-item standard measure, the EORTC QLQC30: "Has your physical condition or medical treatment caused you financial difficulties in the past year?" and using an 'any-or-none' composite measure of 22 items assessing financial difficulty, worries and the use of cost-coping strategies. Multivariable logistic regression models assessed the association between financial difficulty, diagnosis, and socioeconomic and treatment characteristics. 16.8% reported experiencing financial difficulty using the single-item measure and 60.3% using the composite measure. Most frequently endorsed items in the composite measure were financial worry about having to pay large medical bills related to cancer and difficulty paying medical bills. Financial difficulty using the single-item measure was associated with having MM versus CLL (adjusted odds ratio [aOR], 0.34; 95% CI, 0.13-0.84; P=.02), having insurance other than Medicare (aOR, 2.53; 95% CI, 1.37-4.66; P=.003), being non-White (aOR, 2.21; 95% CI, 1.04-4.72; P=.04), and having a high school education or below (aOR, 0.36; 95% CI, 0.21-0.64; P=.001). Financial difficulty using the composite measure was associated with having a high school education or below (aOR, 0.62; 95% CI, 0.41-0.94; P=.03). U.S. patients with blood cancer report financial difficulty, especially those with low socio-economic status. Evidence-based and targeted interventions are needed.