Although Pseudomonas chlororaphis O6 (O6) is known to be a rhizobacterium capable of inducing systemic resistance against plant virus, its antiviral products from O6 remain unknown. In the present study, an antiviral cyclic peptide was identified from the cell-free supernatant of O6. O6 cultures grown on Luria Bertani medium were centrifuged, and the resulting supernatant was extracted with organic solvent, followed by a series of column chromatography and preparative high performance liquid chromatography (HPLC). Bioassay-guided fractionations were involved in the isolation of antiviral products against tobacco mosaic virus (TMV). Time of flight mass spectrometry (TOF-MS) analysis of the isolated product detected $(M+H)^+$ peak at m/z 887.4242 that generated m/z 756.3859, 657.3180, 556.2724, 459.2208, 345.1873, and 171.1130 as the main fragment ions. NMR analyses characterized all protons and carbons of the isolated product. Based on the data, the isolated antiviral product was determined to be a cyclic peptide with molecular formula $C_{39}H_{67}N_9O_{12}S$ consisting of seven different amino acids. The antiviral peptide exhibited more than 95% disease suppression of TMV at 1,000 ${mu}g/mL$. O6 may play a role in promoting plant growth.