Although parenteral nutrition (PN) is an important treatment for patients who are unable to tolerate enteral nutrition (EN), recent international guidelines recommended that PN should be reserved and initiated only after 7 days in well-nourished patients. This retrospective study was conducted to analyze the effect on clinical outcomes of a PN protocol with PN starting 4 days after admission to the intensive care unit (ICU). Eighty-one patients who were admitted from January to March of 2012 were included in the pre-protocol group, and 74 patients who were admitted from April to June of 2012 were included in the post-protocol group. There were no significant differences between the two groups when the age, gender, and admission Acute Physiology and Chronic Health Evaluation (APACHE) II scores were compared. Significantly fewer patients in the post-protocol group were provided PN (58.1% vs. 81.3%, p = 0.002), which was initiated significantly later than in the pre-protocol group (2.7 ± 2.2 days vs. 1.9 ± 2.0 days, p = 0.046). Five patients (6.2%) in the pre-protocol group acquired central line-associated bloodstream infection (CLA-BSI) in the ICU, yet none of the patients in the post-protocol group developed CLA-BSI (p = 0.03). The duration of antibiotic therapy and ICU stay were significantly shorter in the post-protocol group than in the pre-protocol group. By delaying initiation of PN, short-term clinical outcomes including incidence of CLA-BSI, antibiotic use, and ICU stay might be improved. Further research should be conducted to investigate the long-term effects of the decreased nutrient intake resulting from delayed PN.