Abstract: The importation of Litopenaeus vannamei to Iran from Hawaii was initiated when Iranian shrimp culture was first affected by WSSV in 2004. The main reason for the importation of L. vannamei to Iran was the disease susceptibility and mass mortality of the indigenous species (P. indicus) when faced with the first outbreak of WSSV. During the two years of study, it was found out that culturists in Iran preferred cultured L. vannamei than the local species (P. indicus). In 2008, mass mortality occurred in farmed L. vannamei in Khuzestan Province South of Iran. Two hundred shrimps with white spot on the carapace and body were collected and preserved in Davidson fixative for histopathology. A part of samples collected were also preserved in 95% ethyl alcohol for Polymerase Chain Reaction (PCR) technique. Two pair primers from VP24 WSSV genome was identified and used for PCR while identified one pair primer for 18SrRNA gene of shrimp was used as house keeping gene in PCR reaction in both positive and negative PCR reaction. Grossly, the samples showed white spot in the cuticle and body surface and red color on the appendages. Histopathologically, all tissue except hepatopancreas showed the intranuclear Cowdry type-A inclusion bodies. PCR studies using designated primer revealed a band of 414 bp from WSSV and 809 bp of shrimp DNA fragments in positive samples. The negative samples showed just 809 bp. This is the first report of White Spot Syndrome Virus (WSSV) in farmed L. vannamei in Iran.