Atrial fibrillation is one of the most frequently encountered arrhythmia, with obesity being an independent risk factor. There are sparse data on the success rates of direct current cardioversion (DCCV) in patients with severe obesity. We compared the effectiveness of DCCV in patients with a body mass index (BMI) >50 kg/m² with those with a BMI <30 kg/m². A retrospective chart review of 111 patients was performed between January 1, 2011 and January 1, 2022. The study cohort was stratified into 2 groups: BMI ≥50 kg/m² and BMI <30 kg/m². The primary outcome was successful achievement of normal sinus rhythm after DCCV. The secondary outcomes included number of attempted shocks, number of successful shocks on first attempts, and energy of successful shock. The primary outcome occurred in 94.6% of patients with a BMI <30 kg/m² group compared with 81.8% in the patients with a BMI ≥50 kg/m² (p = 0.042). Patients in the higher BMI cohort had a higher median energy during a successful shock than the lower BMI cohort (250 J [200 to 360 J] vs 200 J [150 to 200 J], p <0.001). There was no difference in the number of shocks used between the 2 groups or in the success of the first shock delivered between BMI ≥50 kg/m² and BMI <30 kg/m² (75% vs 58.2%, p = 0.093). In conclusion, patients with a BMI ≥50 kg/m² had lower rates of successful DCCV than patients with a BMI <30 kg/m²; therefore, clinicians must be aware of the alternative strategies to improve DCCV success and the possibility of DCCV failure in patients with higher BMIs.