Purpose: Neonatal sepsis is an important cause of morbidity and mortality. The signs and symptoms of neonatal sepsis are nonspecific, and there is no ideal marker for diagnosis. Our study aimed to investigate the role of platelet indices in determining agents in sepsis. Materials and Methods: A total of 90 records with sepsis data were examined retrospectively, demographic and clinical characteristics of gram-positive, gram-negative and Candida infection patients were evaluated by complete blood counts at the time of diagnosis and on the fifth day of infection and platelet amount (PLT), mean platelet volume (MPV), plateletcrit (PCT) and distribution width (PDW) values were compared by ROC curve analysis. Results: No statistical difference was found between the groups in terms of gender, gestational week, birth weight, surfactant use, need for mechanical ventilator treatment, and necrotizing enterocolitis. When infection was first detected, the Area Under Curve (AUC) of PCT, PLT and MPV (without thrombocytopenia) values in detecting gram-positive bacterial infection were 0.764, 0.765 and 0.792 respectively. Conclusion: The increase in PCT and PLT values at the time of initial diagnosis can be used to detect gram-positive bacterial infections. A decrease in MPV can be used for early diagnosis of fungal infections without thrombocytopenia.