Background: COVID-19 disease, which spreads all over the world, is a disease characterized by widespread inflammation and affects many organs, especially the lungs. The resulting inflammation can lead to the generation of reactive oxygen radicals, leading to oxidative DNA damage.Methods and Results: Pneumonia severity of a total of 95 hospitalized patients with positive RT-PCR test was determined and divided into three groups mild, moderate, and severe/critical. Inflammation markers (Neutrophil-lymphocyte ratio, serum reactive protein, procalcitonin, etc.) were determined, and IL-10 and IF γ measurements were analyzed using the enzyme-linked immunosorbent assay method. In the evaluation of oxidative damage, total thiol, native thiol, disulfide, and IMA levels were determined by measuring spectrophotometrically. The percentage of tail DNA obtained by the comet assay method was used to determine oxidative DNA damage. As a result, when mild and severe/critical groups were compared, we found that total thiol, native thiol, and disulfide levels decreased significantly in the severe/critical group due to the increase in inflammation markers and cytokine levels (p <0.05). We could not detect any significance in IMA levels between the groups (p> 0.05). At the same time, we determined that there was an increase in the tail DNA percent level, that is, DNA damage, due to the increased oxidative effect.Conclusion: As a result, we found that increased inflammation and reactive oxygen species due to the increase in pneumonia increased in those with severe and severe pneumonia, which in turn damaged DNA. We think that it would be useful to follow up on the DNA damage in these patients in terms of neurodegenerative diseases and cancer development.