Background: Our goal is to study the hematological changes in Covid-19 and the relation between these changes and the progression of the disease. Methods: It combined a retrospective and prospective study at the isolation unit of Covid-19 department of Benha Children Hospital. The time frame for this research was from January of 2021 through December of the same year. All patients diagnosed with COVID-19 or Multisystem inflammatory syndrome in children (MIS-C) /Kawasaki, were included in the study. Results: This study included 300 patients who were divided into two groups based on their PCR results. Group I: negative PCR group (223 patients). Group II: positive PCR group (77 patients). Mean age was statistically significantly higher among negative COVID 19 group than positive group (p=0.03). Mean HB and HCT % were statistically significantly higher among negative COVID 19 group than positive group (p=0.02 and 0.03 respectively), Mean D-dimmer, Sferritin and L D H were statistically significantly higher among positive COVID 19 group than negative group (p<0.001). Contact with a probable, confirmed or linked to cluster results, was statistically significantly higher among positive COVID 19 (58.4%) group than negative group (14.8%) (p<0.001). Less than 1 year old age was statistically significantly higher among positive COVID 19 (61%) group than negative group (45.7%) (p=0.02). Conclusion: Diagnosing COVID-19 and determining prognosis may be aided by testing blood parameters. Shifts in the lymphocyte count are not readily apparent in children. However, D-dimer levels are elevated in COVID-19-infected children. Abnormal hematological parameters are one way in which COVID-19 might manifest itself, and they can serve as early evidence for diagnosis and prognosis.