We examined the effect of AF a commonly encountered arrhythmia with significant morbidity on mortality following a motor vehicle accident (MVA) related hospitalization.The Nationwide Inpatient Sample (NIS) was queried to identify patients with AF (ICD-9 CM 427.31) and MVA (ICD-9 CM E810.0-E819.9), considered separately and together, from 2003 through 2012. Baseline characteristics were identified and multilevel mixed model multivariate analysis was employed to verify the impact of AF on in-patient mortality in survivors.Of an estimated 2,978,630 MVA admissions reported, 79,687 (2.6%) hospitalizations also had a diagnosis of AF. The in-hospital mortality was 2.6% in MVA alone and 7.6% in MVA and AF. In multivariate analysis, after adjustment for age, gender, Charlson Comorbidity Index (CCI), the Trauma Mortality Prediction Model (TMPM), and hospital characteristics, AF was independently associated with in-hospital mortality [Odds ratio (OR) 1.52, confidence interval (CI) 1.41-1.69, P value<0.0001]. In patients with MVA and AF, increasing age, CCI, and TMPM were associated with higher mortality. Female gender is associated with lower mortality (OR 0.84, CI 0.81-0.88, P -0.0016). Most patients with MVA and AF had a CHADS2 score of 2 (34.6%). Mortality and transfusion rates were higher in MVA and AF patients compared to patients with MVA alone across all CHADS2 scores.In patients with a MVA, the presence of AF is an independent risk factor for in-hospital mortality.