The distribution and abundance of estuarine mysids throughout the South-west to North-west region of Sri Lanka were studied during March 2012 to July 2013. Surveys were conducted along the boundary of the estuaries, during daytime, using a dip net (mesh size 500 μm., opening 25×20 cm2). Four mysid species were identified, Mesopodopsis orientalis, Mesopodopsis zeylanica, Sirella srilankensis (new) and Anisomysis srilankensis (new). Mesopodopsis orientalis was the most widespread taxon and most common species in North-west coast and showed abundance in Puttalam, Mannar, Arippuwa, Mundal and Kalpitiya. Mesopodopsis zeylanica and S. srilankensis were distributed in both West and North-west cost. Mesopodopsis zeylanica was the most abundant species in Negombo, Bolgoda, Achchankulam and Chilaw. Anisomysis srilankensis were recorded only from Kalpitiya lagoon. Mesopodopsis zeylanica was confined to lower salinities and lower temperatures. Sirella srilankensis and M. orientalis occurred within wider salinities. Salinity, temperature and pH influenced the variation in mysid abundance. Mysids were abundant in shady areas where widely distributed mangroves present as boundary vegetation. They were not found in; sites with pollutants, where no mangroves or newly filled boundaries or concrete boundaries, where Eichhornia crassipes available. The condition of the estuarine boundary, especially marginal vegetation, play an important role in the occurrence of mysids.