To evaluate the transfusion rates for octogenarians and nonagenarians following total knee and hip arthroplasty (TKA, THA), we compared transfusion rates and associated risk factors among sexagenarians, septuagenarians, octogenarians, and nonagenarians. This retrospective cohort study included 13,603 sexagenarians, 9796 septuagenarians, 2706 octogenarians, and 158 nonagenarians that received a primary, unilateral THA or TKA between 2016 and 2020 at a high-volume institution. Using multivariable logistic regression analysis, the study analyzed risk factors for postoperative transfusions including use of tranexamic acid (TXA) and compared preoperative and postoperative hemoglobin (Hgb) levels and the drop in Hgb. Nonagenarians had significantly higher transfusion rates (THA 25.5%, TKA 26.7%) than octogenarians (THA 9.9%, TKA 9.2%), septuagenarians (THA 3.3%, TKA 4.5%), and sexagenarians (THA 1.9%, TKA 2.9%) (P < .01). Significant risk factors for transfusion requirement following THA were American Society of Anesthesiologists level III (odds ratio [OR] 5.3, P < .01) and American Society of Anesthesiologists level IV (OR 8.0, P= .01), nonuse of TXA (intravenous: OR 0.3, P < .01; topical: OR 0.5, P < .01), lower preoperative Hgb levels (OR 0.4, P < .01), longer duration of surgery (OR 1.0, P < .01), and hepatopathy (OR 3.1, P < .01). Significant risk factors following TKA were nonuse of TXA (intravenous: OR 0.3, P < .01; topical: OR 0.5, P < .01; combined: OR 0.2, P < .01), lower preoperative Hgb levels (OR 0.4, P < .01), and longer surgery time (OR 1.0, P < .01). The strongest independent risk factors for increased transfusion rates among octogenarians and nonagenarians were lack of TXA application and lower preoperative Hgb levels. Routine TXA application and preoperative patient optimization are recommended to reduce transfusion rates in patients aged 80+.