Purpose: Attending physicians in Korea are aware of the existence of the Nutrition Support Team (NST), but even when the NST are consulted, compliance with their recommendations may be low. This study was performed to identify physicians’ compliance with the NST advice and how this affected the outcome of treatment for critically ill patients. Methods: This study was a retrospective observational study. Critically ill patients who were older than 18 years, younger than 90 years, and had been admitted and managed in the intensive care unit were selected for this study. Patients were assigned to either the compliance group or the non-compliance group according to physician compliance with the NST advice. Each group were compared using variables such as calorie supply, protein supply, laboratory findings, hospital stay, 30-day mortality, and survival rate. Results: The compliance group (81% of cases) was supplied with a significantly higher energy (1,146.36 ± 473.45 kcal vs. 832.45 ± 364.28 kcal, p < 0.01) and a significantly higher protein (55.00 ± 22.30 g/day vs. 42.98 ± 24.46 g/day, p = 0.04) compared with the non-compliance group. There was no significant difference in the basic demographics between groups, although the compliance group had a better outcome in the 30-day mortality rate (8% vs. 26%, p = 0.02), and in survival beyond 1 year (Crude model, hazard ratio: 2.42, CI: 1.11-5.29). Conclusion Critically ill patients whose attending physician complied with the NST advice, received an increased energy intake and supply of protein which was positively associated with survival.