The Pacific oyster , Crassostrea gigas, is the most cultured oyster around the world, thus it is also widely distributed as invasive. Recently it has increased its distribution in the Northeastern Pacific coast, especially in Southern California and Baja California. In order to understand the effect of these invasive species on coastal habitats, we first need to know their distribution and abundance. In order to understand the extent of the invasion in Northwest Mexico , we sampled 6 open estuaries in the northern Pacific coast of the Baja California Peninsula from La Bocana (26°N), Baja California Sur, to Estero de Punta Banda (31°N), Baja California. In 2019 and 2020, w e sampled 2-5 sites per estuary using a 1m2 quadrat every 5 m on a 50 m transect to count live oyster s and empty shells. We found that the Pacific oyster, Crassostrea gigas, is widely distributed and is as abundant than native oysters in many estuaries (Fig. 1) .