A 56-year-old woman from Brazil was diagnosed with a co-infection of SARS-CoV-2 and dengue virus (DENV). She tested positive for both viruses simultaneously via RT-qPCR. Researchers believe that the patient was initially infected with SARS-CoV-2 and then infected with DENV shortly afterward. Fortunately, the patient did not develop severe COVID-19 or severe DENV. This case report confirms the possibility of co-infection, indicating that the diagnosis of one infection should not neglect the potential of being infected with another illness, particularly in countries with high infection rates of multiple viruses.