Background and Aim: Because COVID-19-affected individuals with severe disease are more susceptible to develop acute respiratory distress syndrome, metabolic acidosis, and septic shock, it is currently widely accepted that severe COVID-19 cases have a higher fatality rate than mild instances. Hence, it is very critical to identify between severe and mild disease among the COVID-19-affected individuals at the earliest to prevent the fatal sequelae. The study was done using serum ferritin and D-dimer levels as biomarkers to find a correlation between the severity of lung involvement among COVID-positive patients. Materials and Methods: A cross-sectional study has been conducted between June 2021 and November 2021 for 6 months among the patients who are positive for COVID-19 at the Government Erode Medical College. Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) was detected in all of the patients using a real-time reverse transcription–polymerase chain reaction assay. Results: One hundred and eight COVID-19-affected individuals with lung involvement and 102 COVID-19-affected individuals without lung involvement were included in the current study. Groups A and B had mean ages of 61.72 ± 10.6 years and 54.78 ± 12.4 years, respectively. COVID-19 infection was studied in patients who were both mildly unwell and severely ill, where the findings revealed a link between serum ferritin and D-dimer levels and lung involvement among COVID-positive patients. The group with lung involvement had considerably higher D-dimer levels than the group without the involvement. Conclusion: The levels of D-dimer and ferritin are linked to serious involvement of the lung as indicated by the computed tomography scan. Both these markers of inflammation are useful in determining the severity of SARS-CoV-2 infection among the infected patients.