Background: Monthly out-of-pocket costs (OOPC) for Ontario patients with cancer have previously been reported, but little detail has been provided on differences based on tumour type. Methods: A questionnaire administered in cancer clinics in the province of Ontario, with a mix of urban and rural patients, was analyzed using descriptive statistics and a regression analysis of cross-sectional data. The dependent variable was OOPC (Canadian dollars), analyzed separately for total OOPC (excluding imputed travel costs), and for each of the individual cost categories. Results: Compared with colorectal, lung, and prostate cancer patients combined, breast cancer patients had statistically significantly higher total OOPC ($393 vs. $149, p = 0.02), device costs ($142 vs. $12, p = 0.018), and family care costs ($38 vs. $3, p = 0.01). By contrast, they trended toward lower costs for travel ($225 vs. $426, p = 0.055) and had lower costs for parking ($32 vs. $53, p = 0.0198). Compared with non-breast cancer patients, patients with breast cancer reported a greater perceived financial burden (31% vs. 17% p = 0.0133). Interpretation: These findings highlight that financial burden for cancer patients can vary by tumour type, and that patients with breast cancer may require a different mix of supportive services than do patients with other common tumour types. Supportive care programs related to financial burden should consider the likelihood and nature of financial burden when counselling breast cancer patients.