Objective: To investigate the association between reduced phase angle values and the deterioration of hospital outcomes in colorectal cancer (CRC) patients undergoing surgery. Data sources and methods: This retrospective study was conducted at the Surgical Clinic of KBC Split, including 422 patients who underwent surgery for CRC between March 1, 2021, and February 29, 2024. Data were collected from electronic databases and analyzed statistically. Primary outcomes included length of stay, rehospitalization rates, mortality, and costs, while secondary outcomes involved complications according to the Clavien-Dindo classification. Results: The median age of patients was 69 years, with 37.4% being women. The most common surgeries performed were right hemicolectomy (157), left hemicolectomy (41), and sigmoid, rectum, and rectosigmoid resections (185). Laparoscopic approach was used in 132 cases (with a 10.6% conversion rate to open surgery). Most patients had T3 tumors (59%), and 40% had disease spread to regional lymph nodes. Cox regression analysis identified four predictors of mortality: age, phase angle of bioelectrical impedance, fat mass, and fall risk according to the Morse scale. An increase in phase angle by 1° reduced the mortality risk by 4.45 times. The risk model had an AUC of 0.837, with 100% sensitivity and 66% specificity. Survival within the first 30 days after surgery was 100% for patients without risk, while it was only 36.6% for high-risk patients (P = 0.006). The median postoperative stay was 7 days. Laparoscopic surgery shortened the stay by one day. Longer stays were observed in patients with higher risk for decubitus ulcers and complications. An increase in phase angle by 1.15° reduced the length of stay by one day. The 30-day rehospitalization rate was 11.6%, with higher rates among men (75.5%). The highest rehospitalization rate was observed after rectal amputation (20.8%) compared to right hemicolectomy (8%). Laparoscopic approach reduced the need for rehospitalization, but the difference was not statistically significant (P = 0.055). Conversion from laparoscopic to open surgery was significantly more frequent in patients readmitted (21.1% vs 4.8%, P = 0.007). The median treatment cost was 2697 EUR, with extreme costs (>5685 EUR) recorded in 4.3% of cases, linked to length of stay, complications, and rehospitalization rates. The lowest costs were for right hemicolectomy (2107 EUR), while laparoscopic resections of the rectosigmoid were 443 EUR more expensive. Discussion & Conclusions: The phase angle of bioelectrical impedance is a significant predictor of key treatment outcomes, as are other BIA measurements (e.g., fat mass). However, the differential impact of phase angle on hospital outcomes largely depends on the type of surgery and surgical approach. Further research in balanced cohorts is needed to clearly define the potential impact and predictive value on these outcomes.