BACKGROUND: In observational studies, case reports, and animal studies, amiodarone has been associated with incident cancer. OBJECTIVE: The purpose of this study was to examine whether a dose-response relationship between amiodarone use and the risk of cancer could be ascertained in a large nationwide study cohort. METHODS: Using nationwide registers, we included all Danish patients with atrial fibrillation (AF) treated with amiodarone from 1996 to 2014. Exposure was defined both by categories and as a continuous variable of the cumulative defined daily doses (cDDDs) of amiodarone. The associations between amiodarone cDDD and incident cancer, as well as organ-specific types of cancer (skin, liver, lung), were estimated using multivariable Cox regression models and reported as hazard ratios (HR) with 95% confidence intervals (CI) and using cubic restricted spline plots. RESULTS: We included 18,503 patients with a median follow-up time of 8.1 years (interquartile range [IQR] 4.3-12.4). Median age was 70 years (IQR 63-77). A total of 2974 individuals developed cancer during follow-up. We found no association between increasing amiodarone exposure (cDDD 181-400 and cDDD >400) and the hazard of incident cancer (HR 0.95; 95% CI 0.87-1.04; and HR 1.01; 95% CI 0.92-1.10) with reference to patients with cDDD <181. Similar results were found when investigating specific cancer types (skin, liver, and lung) as well as cDDD as a continuous variable. CONCLUSION: In a large nationwide cohort of AF patients treated with amiodarone, we found no evidence of a dose-response relationship between cumulative dose of amiodarone and incident cancer risk.