Purpose: The goal of our review was to gather information on the most important community-acquired and hospital-acquired co-infections among coronavirus disease 2019 (COVID-19) patients, and to examine not only the effect of these co-infections on disease outcomes but also to identify the possible risk factors that predispose COVID-19 patients to co-infections. Methods: Medline (PubMed) and Google Scholar were searched for relevant articles published between January 1st, 2020, and September 31st, 2021, on the topic of co-infections among COVID-19 patients. Results: Among community-acquired and hospital-acquired co-infections, bacterial and fungal co-infections are equally frequent, followed by viral co-infections that affected a relatively smaller portion of patients. Overall, co-infections were more frequent in the hospital than at the community level. Risk factors for acquiring co-infections include male gender, longer length of hospital stay, presence of supportive treatment, such as ventilation, the admission to intensive care units, the administration of medications, such as steroids or antibiotics, and certain blood parameters, such as high C-reactive protein or lymphopenia. The presence of co-infections could aggravate the COVID-19 disease severity, prolong the healing time of patients, and lead to worse disease outcomes overall. Conclusion: Co-infections may increase the mortality of COVID-19 patients, especially in the hospital setting. Paying closer attention to hygiene, adhering to diagnostic and therapeutic protocols, implementing antimicrobial stewardship programs could decrease the occurrence of co-infections and lead to improved outcomes for COVID-19 patients. Kulcsszavak: COVID-19 disease, community-acquired, healthcare-associated, co-infection, death rate