We report the first record of the colonial tunicate Clavelina lepadiformis (Muller, 1776) in the northwest Atlantic. Populations were found along the eastern Connecticut shoreline in October 2009. At one site C. lepadiformis had a mean percent cover of 19.95% (±4.16 S.E.). A regional survey suggests that the invasion is relatively localized. Genetic analysis confirms our morphological identification and places the introduced population in the previously described ‘Atlantic clade’. While it appears Clavelina lepadiformis is currently in the incipient stage of introduction in eastern Connecticut waters, its spread to other areas in the region could lead to competition with resident members of shallow water epifaunal assemblages and shellfish species.