Key summary pointsAim To identify if nonagenarians having a total hip or knee arthroplasty are associated with a higher incidence of mortality and morbidity compared to octogenarians. Findings Nonagenarians show higher risk of 1-year mortality and perioperative complications compared to octogenarians after total hip or knee arthroplasty. No difference between nonagenarians and octogenarians is detected regarding the in-hospital mortality, the 30-day readmission rate and the length of hospital stay. Message After total hip or knee arthroplasty, nonagenarians are at greater risk of developing postoperative complications than octogenarians. Meticulous preoperative screening, proper patient selection and optimization of comorbidities are essential to minimize any postoperative side effects in patients over 90 years of age. Purpose Advancing age is a significant risk factor for the development of perioperative complications and mortality in patients undergoing total hip or knee arthroplasty (THA or TKA) due to their compromised health status and the associated medical comorbidities. The purpose of this review is to identify if nonagenarians having a THA or TKA are associated with a higher incidence of mortality and morbidity compared to octogenarians. Methods Medline, Scopus, and the Cochrane library were searched for relevant studies. The primary outcome of the review was the incidence of mortality. The secondary outcomes were the 30-day readmission, the perioperative complications, and the length of hospital stay (LOS). Results Six studies with 479,630 patients were included in the review. No difference between nonagenarians and octogenarians was detected regarding the in-hospital mortality, the 30-day readmission rate, and the LOS. However, nonagenarians were associated with a greater 1-year mortality rate (OR: 2.4; 95% CI 1.91-3.01, P < 0.001; I-2 = 0%) and increased odds of perioperative complications (OR: 1.6; 95% CI 1.48-1.72, P < 0.001; I-2 = 0%). This finding was unchanged after adjusting for baseline characteristics (ORadj: 1.68; 95% CI 1.53-1.84, P < 0.001; I-2 = 0%). Conclusion Although nonagenarians undergoing TKA or THA can achieve the same clinical benefit as octogenarians, they have a higher risk of perioperative complications and 1-year mortality. Therefore, meticulous preoperative screening, proper patient selection and optimization of comorbidities are essential to minimize any postoperative side effects in patients over 90 years of age.