Coronavirus disease (COVID-19) and pulmonary tuberculosis (TB) can both emerge with similar clinical presentations. Despite their different nature of progressivity, both diseases may show similarity in an acute manner, especially in the presence of secondary infection, e.g., TB. This is particularly substantial in TB/HIV-coinfection, with a myriad of possible secondary infections and different clinical presentations. These includes diagnostically challenging Pneumocystis carinii pneumonia (PCP), one of the most common opportunistic infections in TB/HIV patients. Here, we reported a case of an opportunistic infection mimicking COVID-19 in a TB/HIV-infected patient. A 22-year-old female presented to our hospital with decreased consciousness, shortness of breath, and cough. Lab results showed lymphocytopenia and thrombocytopenia as well as elevated C-reactive protein, D-dimer, and ferritin, which is classically suggestive of COVID-19 infection. She was diagnosed with probable COVID-19, but two subsequent consecutive RT-PCR tests for SARS-CoV-2 were negative. Both sputum GeneXpert MTB rapid molecular test and HIV immuno-serology rapid test were positive, and chest X-ray showed bilateral miliary infiltrates. Therefore, the patient was diagnosed as TB/HIV with secondary opportunistic infection. As both COVID-19 and TB/HIV with opportunistic infections can present similarly debilitating risk for the patient, we highlight the importance of accurate history-taking and rapid RT-PCR test for SARS-CoV-2 to ensure accurate and timely diagnosis.