Cyclophilin A (CypA) is a key member of immunophilins that has peptidyl-prolyl cis/trans isomerase (PPIase) activity. Besides acting as a cellular receptor for immunosuppressive drug cyclosporine A (CsA), CypA is involved in various cellular activities. CypA has an important role in viral infection which either facilitates or inhibits their replication. Inhibition of CypA via inhibitors is useful for overcoming several viral infections, indicating that CypA is an attractive target for anti-viral therapy. Collectively, these facts demonstrate the critical roles of CypA in mediating or inhibiting viral infections, suggesting that CypA can be an attractive cellular target for the development of anti-viral therapy.