Abstract. Rimelahas WL, Mulya MB, Barus TA. 2022. Density, morphometric characteristics and distribution pattern of Asiatic hard clam (Meretrix meretrix) in Karang Gading estuary, Deli Serdang District, Indonesia. Biodiversitas 23: 5210-5216. Asiatic hard clam (Meretrix meretrix) has a wide distribution, ranging from mangrove forest areas in the Indo-Pacific to mangrove swamp areas in South America. In Indonesia, clam is found on the island of Sumatra, one of which is in the estuary waters of the Karang Gading Wildlife Sanctuary, Deli Serdang District, North Sumatra, Indonesia. In this area, fishermen are often found catching clams. The catch of clams in addition to its own consumption is also widely sold in traditional markets. The existence of clam capture activities carried out continuously can threaten the sustainability of this commodity in nature. This study aims to find out the density, morphometric characteristics, distribution patterns and the relationship of clam density with aquatic physicochemical. Sampling was carried out in July-August 2021 in the estuary waters of Karang Gading Wildlife Sanctuary Deli Serdang District using a purposive sampling method. Sampling was done by using a clam rake with a radius length of 35 cm. At each station, 5 sampling points were determined and 3 dredgings were carried out at each point which is done 2 times with 30-day intervals at 07.00-11.00 WIB. The results concluded that the highest density of clam is found in station I with a value of 3896 ind/m2, the pattern of growth of the clam at each station is negative allometric, the pattern of the group and uniform clam distribution, and the correlation of physical and chemical factors of the waters with the density of the clam shows that phosphate has a very strong correlation to the density of the clam, while the temperature correlates moderately with the density of the clam.