Background: Though most Iraqi patients who are infected by COVID-19 only suffering from mild symptoms, but in some cases a patient’s condition deteriorates, leading to a negative outcome. This study aims to assess the clinical laboratory features of moderate and severe COVID-19 patients Methods: One hundred diagnosed as moderate and severe COVID-19 patients as well as fifty healthy participants were involved in our current study. Assessment was made for WBCs, Monocytes, Lymphocyte, and Platelets. In addition, serum levels of lactate dehydrogenase (LDH) and C-reactive protein (CRP). Results: A hundred patients aged 33 to 70 years with COVID-19 had severe and moderate cases. Present in DAR AL-SALAM for COVID-19 isolation in Baghdad, Iraq. COVID-19 patients showed increased serum levels LDH and CRP as well as WBCs count and others when compared to healthy individuals. The severe group showed a statistically significant increase in WBCs account, neutrophil activity and LDH levels, compared with moderate group. While the moderate COVID-19 groups displayed a significant rise in lymphocytes activity, CRP, and Platelet. Conclusion: The current investigation found that WBC count, lymphocyte count, LDH activity, and CRP level were effective indicators for determining the severity of COVID-19, making them good assessment indicators.