Infectious diseases are caused by microorganisms and can be transmitted directly or indirectly from one person to another. With direct effects or complications they cause, infectious diseases such as febrile diseases, syphilis, brucellosis, malaria, Lyme Disease, herpes simplex virus, hepatitis, human immunodeficiency virus, rabies and coronavirus disease (COVID) can cause psychiatric symptoms. Medicines such as mefloquine and interferon used in the treatment of infectious diseases can also cause psychiatric symptoms. Infectious diseases such as influenza A viruses and toxoplasma gondii parasite can be present in the etiology of some psychiatric diseases such as schizophrenia. Psychiatric disorders can also facilitate the spread of infectious diseases. As we have seen in the COVID-19 outbreak, global spread of infectious diseases is called a pandemic. During and after the pandemic, the frequency of psychiatric symptoms increases due to the direct effects of the pandemic or, quarantine and social isolation applied due to the pandemic. These symptoms include depressive symptoms, sleep disturbances, anxiety, obsessive symptoms, irritability, loneliness, helplessness, and post-traumatic stress symptoms. There is a high comorbidity between infectious diseases and psychiatric diseases, and clinicians should always consider this condition in epidemics and later periods.