Watermelon mosaic virus (WMV) is member of the genus Potyvirus in the family Potyviridae. To stady determine distributio and phylogenetic analysis this virus in cucurbits various fields of East Azarbaijan and West province, 305 plant samples suspected to be infected were collected from thriteen regions.The sample expressed various symptoms including mosaic, stunting, leaf blistering and deformation. Inoculation were done on the diagnostic hosts and propagation hosts cucurbita pepo. Two weeks after inoculation, WMV isolates caused various symptoms including leaf deformation, thin and torn with green blistering and mosaic on the leaf of Cucurbita pepo. Viral RNA was extracted from infected plant according to Rouhani et al’s protocol and cDNA was prepared. RT-PCR reaction was performed on 54 samples selected as representative of the samples, in terms of the diversity of symptoms and the region. Using specific primers, 800bp fragment was amplified of coat protein gene area of WMV. PCR products of three WMV isolates was directly sequenced based on the variety of symptoms and the region and was compared containing 780 nt from coat protein gene, along with 19 sequences selected from GenBank. Phylogenetic analysis based on the nucleotide sequence of coat protein gene placed these isolates in three groups where T1.Ahr and 32.Tab isolates of East Azarbaijan were placed next to some isolates from Isfahan, Kerman, Yazd and some European countries into group I. of course, T1.Ahr and 32.Tab isolates and ESF.ES.2 isolates from Isfahan and isolates from Europe were clustered into group I. T5.Nagd isolate of West Azarbaijan and isolates traced from different parts of the world were classified in group II.