Background: Transient tachypnea of the newborn (TTN) is a common but mild respiratory problem seen in late preterm and term newborns. However, it may sometimes cause severe morbidity. Objectives: Therefore, biomarkers that can predict TTN severity may aid the clinician in determining the need for intensive care. Our aim was to identify whether blood gases and complete blood count parameters could be utilized to predict the severity of TTN.s Methods: We retrospectively examined the medical records of newborns (> 37 weeks gestation, > 2000 grams) diagnosed with TTN who were hospitalized in the Neonatal Intensive Care Unit (NICU) of Karabuk University Faculty of Medicine, Training and Research Hospital, Karabük/Turkey between June 2019 and June 2020. Patients were grouped according to the length of stay in the NICU. Group 1 included patients that did not require NICU monitoring after 48 hours, and group 2 included patients who continued to require NICU monitoring after 48 hours. Blood gases and complete blood count parameters were compared between the two groups. Results: During the study period, 91 newborns were hospitalized in the NICU due to respiratory distress. Thirty-nine patients who did not meet the inclusion criteria were excluded. Gestational age and birth weight were significantly lower in group 2 (P < 0.05). There were no significant differences between the groups in terms of leukocyte count, hemoglobin level, mean platelet volume (MPV), and platelet count. Partial carbon dioxide pressure (PCO2) was significantly elevated, and base excess (BE) was significantly greater in group 2. Conclusions: We determined a relationship between a prolonged stay in NICU and the levels of PCO2 and BE among patients hospitalized with a diagnosis of TTN. Therefore, PCO2 and BE values may be valuable to determine the prognosis of TTN in the early period. Despite being one of the most common causes of intensive care admission in the newborn population, there is limited data on the diagnosis, treatment, and prognosis of TTN; thus, we believe that our results will shed light on this problem.