The primary goal of this study was to assess the risk of postoperative surgical and medical complications and problems among nonagenarian patients operated with hip arthroplasty. Data from a specific high-volume arthroplasty clinic, were collected to evaluate postoperative morbidity and complication rates after hip arthroplasty in nonagenarians, compared with a control group of younger, but similar patients. Outcomes evaluated included length of stay, transfusion rate, and postoperative medical and surgical complication rates. A total of 97 nonagenarian patients (mean age 91.4years) were included, and compared with 89 control group patients (mean age 70.18years). Nonagenarian patients had significantly longer length of stay (11.44 vs. 7.98days, p < 0.01), significantly higher risk of needing a transfusion (11.30% vs. 3.40%, p = 0.04), and significantly higher risk of a postoperative medical complication (28.90% vs. 11.20%, p = 0.03). There was no difference in postoperative surgical complication rate (7.20% vs. 2.20%, p = 0.12). Nonagenarian patients, when compared to a younger control group, experience significantly longer hospital stays, and risk of non-surgical complications. Arthroplasty in nonagenarian patients carries with it a high risk of complications, and thus careful pre-operative evaluation and the care of these patients at high volume, specialized clinics is important to optimize outcomes. Level III retrospective cohort analysis.