Background: Transient tachypnea of the newborn (TTN) is a common cause of respiratory distress in late preterm and term infants and is generally a benign disease treated with a brief course of oxygen. Platelets contribute to the basal barrier integrity of the alveolar capillaries, which selectively restricts the transfer of water, proteins, and red blood cells out of the vessels. This study aimed to evaluate the role of mean platelet volume (MPV) in predicting the severity of TTN and its outcome. Methods: This study included 60 neonates. They were divided into two groups; group 1 including 20 newborns with tachypnea for 48 h. Group 2 was subdivided into 2 subgroups; group 2A including 20 newborns who needed only oxygen therapy and group 2B including 20 newborns who needed ventilator support. ROC analysis was done to assess the performance of laboratory investigations associated with tachypnea> 48 hours. Results: Regarding platelet count; AUC was 0.756 (95% confidence interval: 0.634-0.878, p=0.001). At a cutoff point