Corticosteroid therapy to combat inflammation caused by SARS-CoV-2 seems to be a risk factor for developing secondary fungal co-infections. PubMed and ScienceDirect databases were searched, with the following word groups: [(aspergillosis OR mucormycosis OR candidiasis) AND (coronavirus disease) AND (corticoids). The selected articles present the main risk factors related to the establishment of secondary fungal co-infections in COVID-19 patients. Corticosteroid therapy used to combat inflammation caused by SARS-CoV-2 has been shown to be strongly associated with the establishment of mucormycosis and aspergillosis. Mucormycosis has been the main fungal co-infection related to corticosteroid therapy, causing a high number of deaths in COVID-19 patients. Diabetes mellitus was the most prevalent comorbidity, especially for the establishment of mucormycosis. Dexamethasone use seems to be associated with mucormycosis emergence and death. However, aspergillosis showed a greater relationship with patient recovery. Thus, risk factors such as diabetes mellitus, combined with corticosteroid use, have shown a relationship to the establishment of mucormycosis. The corticosteroids used in COVID-19 patients should be individually analyzed, considering the patient’s medical history and the risk/benefit ratio of the use of these drugs.