We present a survey of the bee fauna of Gardiners Island, Suffolk County, NY. The study focuses on more than 10,000 bee specimens collected by net during 1976, 1977, and 2005–2011. These surveys recorded 154 bee species and morphospecies in 30 genera. Bee species associated with fields, beaches, and woody plants were well represented in the sample, whereas those requiring herbaceous understory flowers were relatively few. Notable finds include several species with southern affinities that are otherwise scarce in New York State and paratypes of the social parasite Lasioglossum (Dialictus) rozeni. The newly discovered male of Sphecodes johnsonii is diagnosed and imaged. Two Nomada morphospecies may be undescribed. A single worker of the northern species Bombus (Cullumanobombus) rufocinctus provides the first coastal record for New York State. New records of Dianthidium (D.) simile from nearby Long Island and of Pseudoanthidium (P.) nanum from New York City (and nearby New Jersey) increase the number of bee genera and described species recorded from New York State to 45 and 447, respectively. Phenological data may provide new evidence for host-parasite associations. The bee diversity of Gardiners Island is discussed in relation to the bee fauna of the northeastern US, especially records available for other Atlantic coastal islands in the region.