: To identify transfusion thresholds and risk factors for acute kidney injury (AKI) in gastrointestinal oncology surgery, enhancing early intervention and improving postoperative outcomes. : From 2018 to 2022, 765 patients with gastric or colorectal cancer who underwent major gastrointestinal surgery were retrospectively enrolled. The primary outcome was AKI development within 7 days postoperatively. Clinicopathological characteristics and short-term outcomes were recorded and compared. : Of all enrolled patients, 39 (5.1%) developed AKI. Patients with AKI were predominantly older and had more preoperative comorbidities, lower levels of preoperative hemoglobin and serum albumin, but higher levels of blood urea nitrogen and serum creatinine (SCr). Patients developing AKI experienced higher rates of in-hospital complications (overall: 48.3% vs. 14.2%, < 0.001), prolonged hospital stays (25.4 ± 22.5 days vs. 12.3 ± 7.9 days, < 0.001), increased intensive care unit (ICU) admissions (53.8% vs. 22.5%, < 0.001), and higher rates of 30-day re-admission (13.9% vs. 2.4%, = 0.003). Significant AKI risk factors included age (per 10 years, OR: 1.567, 95% CI: 1.103-2.423, = 0.043), preoperative SCr (per 10 μmol/L, OR: 1.173, 95% CI: 1.044-1.319, = 0.007), intraoperative RBC transfusion (per 1000 mL, OR: 1.992, 95% CI: 1.311-3.027, = 0.001 with a significant surge in AKI risk at transfusions exceeding 1500 mL), patient-controlled analgesia (protective, OR:0.338, 95% CI: 0.163-0.928, = 0.033), and diuretic use (OR: 5.495, 95% CI: 1.720-17.557, = 0.004). : Early intervention is essential for patients with preoperative low perfusion or anemia, with particular emphasis on moderating interventions to avoid fluid overload while carefully avoiding nephrotoxic medications, thereby improving postoperative outcomes.