Several publications have described the laboratory characteristics of COVID-19. Notably, the increase in D-dimer levels was more pronounced in individuals who were seriously ill. The goal of this study was to observe and discover if either D-dimer, CRP, fibrinogen, and IL-6 acted as a mortality predictor in Southeast Asian population, COVID-19 patients treated in the ICU. This was a prospective, observational study. All Southeast Asian ethnic, ≥18 years old patients diagnosed with COVID-19 who were admitted to ICU either during the course of their treatments or upon admission were included in the study. As a routine assessment and follow-up protocol for COVID-19 cases, as per hospital’s ICU protocol, we collected blood samples from our subjects every 12 hours and tested them for CRP, D-dimer, fibrinogen, and IL-6 levels. All-cause in-hospital mortality rate was recorded for outcome. Out of the four variables tested for correlation analysis, only D-dimer was found to be significantly correlated (r= 0.212, p=0.005). Meanwhile, CRP (r=0.137, p=0.070), fibrinogen (r=0.04, p=0.602), and IL-6 (r=0.072, p=0.340) were found not to be significantly correlated with mortality. Receiving operator characteristics (ROC) curve analysis showed that the cut-off points for D-dimer to predict mortality in our study was at 1.27 µg/dL. The cut-off point would yield 84% sensitivity and 56% specificity. The highest serum D-dimer level in the first 48 hours is correlated with mortality. At a 1.27 µg/dL level cut-off point, D-dimer level showed 84% sensitivity and 56% specificity for predicting intrahospital mortality.