New biomarkers are needed to identify Coronavirus Disease 2019 (COVID-19) patients who experience deterioration and have the potential to die. Elevated levels of C-reactive protein (CRP) occur in the early phase of infection when the SARS-CoV-2 virus binds to the ACE2 receptor and infects bronchial epithelial cells. Then, in the hyperinflammatory phase of COVID-19, there was an increase in serum ferritin, where the levels were higher in severe cases of COVID-19. It is recommended that serum CRP and ferritin be tested since they can be used as screening to evaluate the degree of severity and predict the prognosis of COVID-19 in the hospital. This observational study with a cross sectional approach used medical record data at Wahidin Sudirohusodo Hospital. The sample size was 639 people, with 2 subjects excluded due to extreme high levels of CRP and ferritin, thus the number of subjects being 637 people. A significant positive correlation was found between CRP and ferritin levels at all degrees of severity of COVID-19 (p<0.001), where the higher the CRP level, the higher the ferritin level. Based on the value of the correlation coefficient (R), the strongest correlation between CRP and ferritin levels was found in severe cases (R=0.587) and the weakest in very severe cases (R=0.444). CRP levels were positively correlated with ferritin levels at all degrees of severity of COVID-19; the higher the CRP level, the higher the ferritin level.