The aim of this study was to determine the effects of adjuvant immunoglobulin M (IgM)-enriched intravenous immunoglobulin (IVIG) therapy on mortality rate, hematological variables and length of hospital stay in newborn infants with blood culture-proven sepsis. Demographic and clinical features and outcome measures of 63 newborn infants with blood culture-proven sepsis were documented retrospectively from the medical records. The patients were divided into two groups according to their treatment history. The patients in Group 1 received antibiotic therapy only and the patients in Group 2 received both antibiotic and adjuvant IgMenriched IVIG. The study revealed that mortality rates were 28.1% and 12.9% in Group 1 and Group 2, respectively. The mortality rate was lower in Group 2, but the difference between the two groups was not statistically significant (p=0.21). Coagulase-negative Staphylococcus was the most common type of bacteria isolated from the blood culture in both groups. When changing laboratory results were compared between the two groups, hemoglobin, leukocyte count and C-reactive protein levels were different during the first three days of antibiotic treatment. Our study revealed that if diagnosed at an early stage and treated aggressively with appropriate and effective antibiotics, adjuvant IgM-enriched IVIG treatment has no additional benefits in neonatal sepsis.