Objective: To determine the correlation between disease severity and changes in basic hematological parameters in cases of Covid 19 in a tertiary care center.Methodology: This Cross Sectional analytical study was done in Khyber Teaching Hospital from March to June 2020 . Covid-19 cases diagnosed by nasal swab PCR were included in the study. Clinical features were noted by Doctor on duty and Complete blood count was done. Data was analysed by SPSS . Mean and standard deviation were used for quantitative data. Frequency and percentages were used for qualitative data. Shapiro Wilk’s test was done to find normality of the data. Point biserial correlation test was applied to determine association between continuous and dichotomous variables.Levels of hemoglobin leukocyte count and platelet counts in severe cases were shown by box plots.Results: Mean age of 101 cases of Covid-19 was 56±15.7 years. Male to female ratio was 1.5:1. The commonest clinical features were generalized body aches and fever, seen in 53(52.5%) and 48(47.5%) cases respectively. 36 (35.6%) cases were serious and needed ventilatory support. In serious cases, hemoglobin and platelet count were normal in most cases i.e 16(44.4%) and 30(83.3%) respectively, while the leukocyte count was increased in 26 (72%). There was no association between the severity of disease and basic hematological parameters. Conclusion: Leukocyte count is high in cases of Covid-19. There is no significant correlation between severity level and hemoglobin and platelet count. The raised total leukocyte count is associated with severe disease in Covid19.