White tail disease (WTD) is a serious problem in hatcheries and nursery ponds of Macrobrachium rosenbergii in India and many parts of the world. The pathogenic agents have been identified as M. rosenbergii nodavirus ( MrNV) associated with extra small virus (XSV), which is 27 nm and 15 nm in diameter, respectively. Replication of MrNV and XSV was investigated in apparently healthy C6/36 subclone of Aedes albopictus cell line. The results revealed that C6/36 cells were susceptible to these viruses. The replication of these viruses in C6/36 cells was confirmed by RT-PCR, acridine orange staining, infectivity study and electron microscopy. Cytoplasmic ribonucleic acid (RNA) stained by acridine orange increased by 48 h, and by 72 h larger proportion of cells which indicated alterations in quantity and localization of RNA in the infected cells. Post-larvae, challenged by immersion method using inoculum prepared from infected cells, exhibited lethargy, anorexia and opaqueness of abdominal muscle and 100% mortality was observed at 6 days post-infection. Experimentally infected C6/36 cells and post-larvae showed positive by RT-PCR, whereas control cells and healthy post-larvae showed negative. This is the first study to report the multiplication of MrNV and XSV in C6/36 cell line.