127 Background: Poverty and community-level deprivation have been shown to be associated with later stage cancer diagnosis. However, few studies have used objective financial data to study the link between individual financial strain and cancer stage at diagnosis. Our goal was to assess the associations between pre-diagnosis financial strain (FS) as measured by credit reports and later stage cancer diagnosis. Methods: Records from cancer patients diagnosed with solid tumors between 2014 and 2018 from the Western Washington SEER cancer registry and quarterly credit report data from a large credit-reporting agency TransUnion were linked and deidentified. Patients diagnosed with late-stage cancer (stages III and IV) were matched 1:1 to patients diagnosed with early-stage cancer (stages I and II) by age, year of diagnosis, cancer type, and insurance status. We assessed the association between FS (defined as any records of third-party collections, charge-offs, delinquent mortgage payments, tax liens, foreclosures, repossessions, and bankruptcies within 2 years prior to diagnosis) and late-stage diagnosis using conditional logistic regression to account for matching, adjusting for race, sex, marital status, area deprivation, and rurality. We performed stratified analyses by insurance enrollment. Separately, among a subset of unmatched insured breast cancer patients eligible for cancer screening (ages 50-74), we used multivariable logistic regressions to exam how the nonreceipt of screening mammography within 2 years of diagnosis mediated the relationship between FS and late-stage diagnosis. Results: After matching, 27916 patients were included in the analysis (mean age 66, 47% female, 84% White race, 7% Asian or Pacific Islander, 4% Black, and 3% Hispanic). Almost one in three patients (32%) had experienced FS before diagnosis. FS was associated with higher odds of late-stage cancer diagnosis (adjusted OR, aOR 1.18, 95%CI 1.1-1.3), and this association remained significant among insured patients (aOR 1.13, 95%CI 1.03-1.2). Among a subset of insured breast cancer patients (n=6934), FS was associated with nonreceipt of mammography (aOR 1.88, 95%CI 1.5-2.4). The association between FS and late-stage diagnosis became insignificant after we accounted for nonreceipt of mammography (aOR reduced from 1.65 (95%CI 1.4-1.9) to 1.04 (95%CI 0.8-1.4)). Conclusions: FS is associated with a later stage cancer diagnosis, which could in turn lead to adverse cancer outcomes. Among breast cancer patients, this association can be largely explained by nonreceipt of mammography. Our findings suggest that even with insurance coverage, individual’s financial stress may create an additional barrier to timely medical attention for suspicious cancer symptoms or routine screening, further exacerbating cancer disparities. This research highlights the need to develop strategies to improve access to care for these individuals.