The coronavirus, which leads to coronavirus disease 19 (COVID-19), may affect various systems of the body (including respiratory, heart, blood circulation, gastrointestinal, nervous, urinary, and renal systems). Similar to COVID-19, first-and second-hand smoking also endanger the immune system and affect a wide range of systems. Therefore, considering the adverse effects of tobacco on different systems of the body, this study aimed at investigating the effects of tobacco on the onset, transmission, prognosis, and severity of COVID-19 in patients. Related articles were selected through advanced searching in Scopus, PubMed, and ScienceDirect databases and Google search engine while including no time limit and using three keywords derived from Mesh (COVID-19, smoking, and tobacco). Most studies have indicated that the incidence of COVID-19 was extremely lower in patients with a history of active smoking compared to patients with no smoking history. According to the results, smoking has an impact on the prognosis and outcome of COVID-19, increases the severity of the disease, the need for hospitalization and the intensive care unit (ICU), and the death rate, as well as challenging the treatment process and changing the attitude of smokers, enhancing their desire to quit smoking. Therefore, smokers are less likely to develop COVID-19, but the rate of transmission, disease severity, and mortality and the need for hospitalization increase in these subjects, and thus treatment will be challenging. Thus, quitting smoking may help improve the function of the respiratory system.