Viral pathogens are major causes of outbreaks in shrimp farms throughout the world. Monodon baculovirus has been known to be invasive in 85-100% of the shrimp hatcheries, in early or late stages of shrimp. Three-hundred and sixty juvenile of Litopenaeus vannamei with average (±SD) size of 7.99±0.54 g and 3600 post larvae 10-15 were prepared from Shrimp Research Station located in Helleh and 3 hatcheries from Bushehr Province, southern part of Iran, respectively. They were allocated to 9 glass aquariums (50×50×60cm) as 2 groups (postlarvae and juvenile), controls with 3 replications using100 liters well aerated water. They were exposed to MBV as water-born path. Concerning the pathogenesis, three phases were observed. The quantity of intranuclear occlusion bodies was 1-9. Mortality was only observed in postlarvae but not in adult or control groups. It is concluded that MBV can be an invasive pathogen for SPF offspring or postlarvae of L. vannamei being imported to Iran.