Background and Objectives: There are no guidelines for intravenous fluid (IVF) administration after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC). This study assessed rates of post-CRS/HIPEC morbidity according to perioperative IVF administration. Methods: All patients undergoing CRS/HIPEC March 2007 to June 2018 were reviewed, recording clinicopathologic, operative, and postoperative variables. Patients were divided by peritoneal cancer index (PCI), comparing IVF volumes and types administered intraoperatively and during the first 72 h postoperatively. Optimal IVF rate cutoffs calculated using area under the receiver operating characteristic curves and Youden's index determined associations with complications. Results: Overall, 185 patients underwent CRS/HIPEC, and 81 (51%) had low PCI (<10) and 77 (49%) had high PCI (≥10). In low-PCI patients, high IVF rates on postoperative days (POD) #0−2 were associated with higher overall complications: POD#0 (46% vs. 89%, p = 0.001), POD#1 (40% vs. 86%, p < 0.05), and POD#2 (42% vs. 72%, p < 0.05). High IVF rates were associated with respiratory distress (7% vs. 26%, p = 0.02) on POD#0, ileus (14% vs. 47%, p = 0.007) and intensive care unit stay (11% vs. 33%, p = 0.022) on POD#1, and ICU stay (8% vs. 33%, p = 0.003) on POD#2. Conclusions: For low PCI patients undergoing CRS/HIPEC, higher IVF rates were associated with postoperative complications. Post-CRS/HIPEC, IVF rates should be limited to prevent morbidity.