Study on diversity of fishes was carried out from 2007 to 2011 in 13 provinces at 113 sampling sites in the Mekong Delta, Vietnam. A total of 12,946 fish specimen were collected from which total of 292 fish species (188 genera and 70 families) were identified. Results showed that gobies dominated with total of 54 species, followed by cyprinids  with 48 species. The results also indicated that 151 species not share with the other regions of the Mekong; and 67 species newly recorded from the Mekong ang all these species were collected from estuarine and/or mangrove areas. Among the newly recorded species, 62 species were the first records from all-over the Mekong, in which 24 species are the gobies. The results indicated that further study on fish diversity in those habitats are needed and Vietnam Mekong Delta has great reponsibility for the conservation of fish diversity in the particular habitats in the coastal areas such as mangrove areas, mudflats and estuarine areas.