Much has been written about the relationship between high medical expenses and the likelihood of filing for bankruptcy, but the relationship between receiving a cancer diagnosis and filing for bankruptcy is less well understood. We estimated the incidence and relative risk of bankruptcy for people age twenty-one or older diagnosed with cancer compared to people the same age without cancer by conducting a retrospective cohort analysis that used a variety of medical, personal, legal, and bankruptcy sources covering the Western District of Washington State in US Bankruptcy Court for the period 1995-2009. We found that cancer patients were 2.65 times more likely to go bankrupt than people without cancer. Younger cancer patients had 2-5 times higher rates of bankruptcy than cancer patients age sixty-five or older, which indicates that Medicare and Social Security may mitigate bankruptcy risk for the older group. The findings suggest that employers and governments may have a policy role to play in creating programs and incentives that could help people cover expenses in the first year following a cancer diagnosis.