Public health investigators learned of gastrointestinal illnesses in multiple individuals after three separate events were held in June 2013. Illnesses were reported among attendees of a wedding rehearsal dinner held at Wayside Inn in Chatham, MA on June 14, a private birthday party held at the Port Restaurant in Harwich, MA on June 15, and diners at Mattakeese Wharf in Barnstable, MA on June 17. the epidemiologic investigation implicated raw oysters harvested from a single Massachusetts harvester, Chatham Fish and Lobster. Human stool specimens and oysters collected from the harvest bed and from the Wayside Inn were positive for norovirus G1.4.