Background: The progression of COVID-19 has different clinical presentations, which raises a number of immunological questions. Objectives: This study aimed to investigate MMP-9 and TIMP-1 levels in patients diagnosed with COVID-19 and whether the MMP-9/TIMP-1 ratio is associated with lung involvement in COVID-19. Methods: This study was conducted with 192 patients and 45 healthy controls. ELISA was used to measure the MMP-9 and TIMP-1. Results: The MMP-9 and TIMP-1 levels of the patients were found to be higher than those of the controls. MMP-9 and TIMP-1 were detected more in patients with lung involvement on chest CT scans than in those with no lung involvement on chest CT scans. A comparison of lung involvement levels revealed no difference was found between the groups. The MMP-9/TIMP-1 ratio was 5.8 in the group with lung involvement on chest CT scans and 6.1 in the group without lung involvement on chest CT scans. No difference was found between the two groups. A comparison with respect to lung involvement levels showed that the MMP-9/TIMP-1 ratio difference was found between the groups. Conclusion: Diagnostic and treatment methods targeting MMP-9 activity or neutrophil activation may be important in predict-ing lung involvement in COVID-19 and directing clinical outcomes.