Corticosteroids can reduce the mortality rate among patients with severe COVID-19 pneumonia. However, opportunistic infections such as Mycobacterium tuberculosis are of concern, especially among those on high doses of corticosteroids. It is unknown whether the risk of developing subsequent TB infection is high or not among COVID-19 patients on high doses of corticosteroids. Hence, this study was conducted to address this gap of knowledge. We conducted a retrospective, cross-sectional study at the King Chulalongkorn Memorial Hospital from October 12, 2022 to June 30, 2023. Two hundred forty-three participants with documented COVID-19 diagnosis on high dose corticosteroids were enrolled into the study. Baseline characteristics and risk factors of developing TB were collected. The prevalence of TB was significantly different among participants with chronic kidney disease (CKD) stages 2-4 and chronic lung diseases. The incidence of TB post 1-year diagnosis of COVID-19 was 4 out of 243 patients (1.6%) or 1,646 cases per 100,000 person-year. The mortality rate among subsequent TB group was significantly much higher than the non-TB group (50% vs 0.4%; p-value = 0.001). COVID-19 participants on high doses of corticosteroids also were co-infected with other infections such as bacteria (37.1%), fungi (5.3%), and Pneumocystis jirovecii (PJP) (1.2%). We found that the incidence of TB in participants with COVID-19 on high doses of corticosteroids was 11 times higher than the general population. Therefore, we recommend screening for latent TB among these patients to prevent/early diagnose TB disease.