Background and Objectives: The emergence of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to a global pandemic, resulting in significant and far-reaching consequences on life worldwide. Notably, the introduction of new viral variants has brought about clinical manifestations in the paediatric population, some of which exhibit a severe progression. This study aimed to identify essential laboratory parameters crucial for the delineation of an effective therapeutic approach in paediatric patients. Methods: A cohort of 73 paediatric patients meeting the inclusion criteria was selected for this study. Following confirmation of the COVID-19 diagnosis, a thorough analysis of laboratory parameters was conducted, and their correlation with the severity of the illness was examined. Results: Thrombocytopenia, leukocytosis, and lymphopenia demonstrated significant associations with the severity of the disease. Furthermore, vigilant monitoring of D-dimer values was undertaken due to its high correlation with an unfavourable prognosis and the development of a severe form of the disease. Conclusion: This study underscores the utility of D-dimer values and a complete blood count as indispensable parameters in the evaluation of COVID-19 in children. These findings contribute valuable insights into potential avenues for effective therapeutic interventions.