Background: Identifying immune cells involved in COVID-19 disease progression and predictors of poor outcomes is important to manage patients adequately. Methods: A prospective observational cohort study enrolled 53 mild non-hospitalized and 48 hospitalized confirmed COVID-19 patients to a tertiary hospital in Oman. Results: Hospitalized patients were older (58 years vs 36 years, p <0.001) and had more comorbid conditions like diabetes (65 % Vs 21% p<0.001). Hospitalized patients had significantly higher inflammatory markers (p<0.001); C-reactive protein (CRP) (114 vs 4 mg/L), Interleukin-6 (IL-6) (33 vs 3.71pg/ml), lactate dehydrogenase (LDH) (417 vs 214 U/L), ferritin (760 vs 196 ng/mL), fibrinogen (6 vs 3 g/L), D-dimer (1.0 vs 0.3 mcg/mL), disseminated intravascular coagulopathy (DIC) score (2 vs 0) and neutrophil/lymphocyte ratio (4 vs 1.1), (p<0.001). In multivariate regression analysis, statistically significant independent early predictors of ICU admission or death were higher levels of IL-6 (OR 1.03, p=0.03), frequency of large inflammatory monocytes (CD14+CD16+) (OR 1.117, p=0.010) and frequency of circulating naïve CD4+ T cells (CD27+CD28+CD45RA+CCR7+) (OR 0.476, p=0.03). Conclusion: IL-6, frequency of large inflammatory monocytes, and circulating naïve CD4 T cells can be used as independent immunological predictors of poor outcomes in COVID-19 patients to prioritize critical care and resources.