Placobdella ali Huges and Siddall, 2007 has not been reported since its original description based on 3 specimens from Silver Mine Lake in Orange County, New York. The finding of 3 populations of P. ali in Connecticut along with further collection of this species from its type locality facilitated an investigation of host use by this leech, molecular characterization of the species, and observations on its natural history. Placobdella ali commonly occurred on substrate in Silver Mine Lake in Orange County, New York, and Clark's Pond and North Farms Reservoir in New Haven County, Connecticut. A single specimen was found in Lake Wintergreen in New Haven County, Connecticut. Placobdella ali was represented by individuals of a light-colored form and a melanic or dark-colored form. Sequences of 2 mitochondrial genes, CO-I and ND-1, were virtually identical among individuals from Connecticut and New York populations, as well as between the 2 color morphs. Placobdella ali was collected from 10 of 15 (66.7%) American snapping turtles (Chelydra serpentina) in North Farms Reservoir. This observation in conjunction with the absence of P. ali on 55 eastern painted turtles (Chrysemys picta) suggests a fairly high degree of host specificity. Two species of exotic turtles, 3 red-eared sliders (Trachemys scripta elegans), and a single southern painted turtle (Chrysemys dorsalis), which is a state record for Connecticut, indicate the potential of introduction of exotic turtles as a vehicle for the introduction of exotic leeches. One of the 3 (33.3%) red-eared sliders was infested with a single individual of P. ali.