Background: Neonatal diseases are a significant threat to global public health, resulting in the disturbance of normal homeostatic well-being in affected patients and reflecting the status of, and challenges to, regional, national, and global healthcare systems. Objectives: To investigate the disease spectrum observed among neonatal inpatients changed after COVID-19 breakout. Methods: The present hospital-based retrospective study analyzed the demographic and clinical characteristics of 19,943 newborns who were hospitalized from January 2018 to December 2022 using data derived from pediatric department registers. Results: According to the ICD-11 classification criteria, the two most common neonatal disorders during this study period were “Certain conditions originating in the perinatal period” and “Disease of the respiratory system”. Following the start of the COVID-19 pandemic, the number of neonatal patients declined markedly, and the proportion of newborns assigned the “Disease of the respiratory system” ICD-11 classification similarly decreased. Discusssion and Conclusions: The present study retrospectively analyzed these neonatal disease characteristics at our hospital in greater detail, providing a foundation for future research and policymaking efforts.