Background: The purpose of this study was to compare postoperative complication rates in super-obese (SO) patients with a body mass index (BMI) ≥ 50 kg/m 2 undergoing total hip arthroplasty (THA) versus non-super-obese (NSO) patients undergoing THA. Methods: In this retrospective study using the National Inpatient Sample (NIS) database, 1,646 cases of THA in SO (BMI ≥ 50 kg/m 2 ) patients were reviewed. We used International Classification of Diseases (ICD)-10 codes to assess postoperative variables including length of stay, cost of care (cost of inpatient hospitalization), and medical and surgical complications among SO patients undergoing THA compared to NSO patients before being discharged. Results: A comparison of demographic variables showed there were more women in both groups and nearly 17.2% of SO patients were diabetic patients, 11.1% of SO patients were tobacco users, and 74.8% of the SO patients were whites (African American, 15.1%; Hispanic, 2.9%). The mean length of stay was 3.43 days in the SO group and 2.32 days in the NSO group, and this difference was statistically significant. The cost of care was $79,784.64 for the SO group, which was significantly higher than $66,821.75 for the NSO group. The SO group also showed higher odds of developing medical complications such as anemia (odds ratio [OR], 1.555; 95% confidence interval [CI], 1.395–1.734; p < 0.001), acute renal failure (OR, 3.375; 95% CI, 2.816–4.045; p < 0.001), pneumonia (OR, 2.319; 95% CI, 1.241–4.331; p = 0.014), and need for blood transfusion (OR, 1.596; 95% CI, 1.289–1.975;p < 0.001). The SO patients also showed a higher risk of several postoperative surgical complications such as periprosthetic fractures, infection, and wound dehiscence. Conclusions Postoperative complication rates in SO patients were higher than those in the NSO group. Length of stay and cost of care were higher, whereas the mean age was lower for the SO group. Therefore, THA in SO patients should be undertaken only after careful consideration and preferably in a tertiary facility capable of handling all medical and surgical in-hospital complications.