Background: Cannabis is increasingly used by patients with cancer for symptom management but is not covered by insurance and may represent a significant financial burden. We assessed costs of cannabis products for patients who used at any time during cancer treatment. Methods: Adults who received any treatment March-August 2021 for any of 10 cancers (brain, breast, head and neck, gynecological, gastrointestinal, lymphoma, prostate, testicular, and lung) at Memorial Sloan Kettering were identified. Patients residing in New York, New Jersey, or Connecticut (where cannabis use is legal) were invited to complete an anonymous online or phone survey regarding their thoughts and experiences with cannabis. Surveys were administered August 2021-April 2022. Bivariate analysis tested for differences between groups. Weighting was assigned based on demographic/cancer data (age, sex assigned at birth, race, ethnicity, cancer type) of the sampled hospital population to account for potential nonresponse bias. Weighted multivariable logistic regression identified predictors (gender, age, race, ethnicity, income, insurance, marital status, employment status) of cannabis costs. Results: 1258 patients completed the full survey (35% response rate); 278 (22%) endorsed using cannabis products during cancer treatment; 248 (20%) gave cost data and included in this analysis. This subset was 51.2% male and mostly white/non-Hispanic (75%) with 8% Hispanic, 6% non-Hispanic Black, and 8% other/non-Hispanic. 23% were age ≤45, 40% were 45-64, and 29% were ≥65. Most (54%) had income ≥$100,000 and 45% were currently employed. Most (54%) were currently undergoing cancer treatment; most common cancer types were GI (18%), breast (12%), lymphoma (11%), and gynecological and prostate cancer (each 10%). The median monthly out of pocket cost for cannabis was $80 (IQR 25-150). In unadjusted analysis, patients ≤45 (median $100 monthly vs $75 for 45-64 vs $50 ≥65, p = 0.002) and Hispanic patients (median $125 monthly vs $70 white/non-Hispanic vs $60 Black, p = 0.027) paid more for cannabis. On regression analysis, only male gender (OR 2.5, 95CI 1.2-5.5, p = 0.026) and age ≤45 (OR 7.5, 95CI 1.9-30.0, p = 0.0042) were associated with spending ≥$100/month on cannabis. Of the 166 who either stopped using cannabis or used less than they liked since their cancer diagnosis, 28% said it was because the cost is “too high” and 26% said it was because it was not covered by health insurance. Of the 138 who had taken cannabis instead of other medications, only 3% said it was because it was less expensive. Conclusions: Cannabis use during cancer treatment can cause significant out of pocket burden, with men and younger patients more likely to have high cannabis costs. Cannabis expenses may not be captured in standard assessments of medical costs but may contribute to financial toxicity for unknown symptom control benefits.