Little is known about the distribution and ecology of intertidal oysters in northeastern North America. North of Chesapeake Bay, intertidal oysters have either been previously reported as non-existent or only occurring as single oysters or sparse clusters. In the present study, we report the occurrence of dense populations of inter-tidal oysters at several estuarine sites within New Hampshire and mid-coastal Maine, with these growing under dense canopies of the long-lived Ascophyllum nodosum (fucoid alga). The densities of these northern intertidal oysters rival subtidal populations in the same geography, and their sizes suggest a persistence of 5 or more years.