Background: Malignant melanoma (MM), a very aggressive cancer, is associated with the highest mortality rate among dermatologic malignancies. Atrial fibrillation (AF) is the most common cardiac arrhythmia. Very little is reported in the literature on the association between both diseases, and there is marked paucity of studies comparing outcomes in patients with concomitant MM and AF. Methods: Retrospective cohort analyses were performed using the National Inpatient Sample (NIS) data collected between 2016 and 2020. Multivariable logistic and linear regression models were used to examine the predictors of AF and inpatient outcomes among MM patients. Results: Out of 9,760 hospitalizations with a diagnosis of MM, the overall prevalence of AF was 13.3% with an increasing trend from 10.1% in 2016 to 16.4% in 2020. MM patients with AF had similar odds (adjusted odds ratio (AOR) = 0.9; 95% confidence interval (CI) = 0.45?1.61) of inpatient all-cause mortality when compared to those without atrial fibrillation. However, they were more likely to have longer hospital stays (beta coefficient (β) = 1.27; 95% CI = 0.39?2.0) and total hospital charges (β = $12,830; 95% CI: $7041.4?$25426.4) when compared to their counterparts without atrial fibrillation. Furthermore, patients with AF had a double likelihood (AOR: 1.90; 95% CI: 1.25?2.90) of developing an acute kidney injury (AKI). We also found that female MM patients were 50% (AOR: 0.50; 95% CI: 0.36?0.68) less likely to have a diagnosis of AF relative to their male counterparts. Similarly, Hispanic MM patients were significantly less likely (AOR: 0.06; 95% CI: 0.008?0.459) to have AF in comparison to Non-Hispanic White patients. Conclusions: There is an increasing trend of comorbid atrial fibrillation in patients hospitalized for malignant melanoma, and this is associated with longer hospital stays and higher total hospital charges. These findings highlight the need for surveillance to enable early detection of atrial fibrillation in this population.