The milfoil weevil, Euhrychiopsis lecontei Dietz, is a North American herbivore associated with declines of Eurasian watermilfoil (Myriophyllum spicatum L.) in the United States. The weevil is a watermilfoil specialist and northern watermilfoil (M. sibiricum Komorov) is its native host plant. Previous studies have reported better developmental performance (egg to adult development) on Eurasian watermilfoil (exotic host) than on northern watermilfoil (native host). The reported difference in performance between host plants and the weevil’s occurrence in two distinct geographical regions in Washington State (eastern and western Washington) led us to conduct laboratory experiments to compare the developmental performance between weevil and host plant populations. No significant differences were detected in the egg to adult development time for eastern and western Washington weevils reared on Eurasian or northern watermilfoil from both regions. Regional differences, however, were found in egg to pupa development time, number of days spent as a larva, and body size at emergence. Eastern Washington weevils (northern watermilfoil source population) reared on northern watermilfoil from western Washington had significantly longer egg to pupa development time and larval stage than weevils reared on northern watermilfoil from eastern Washington. In addition, eastern Washington weevils reared on northern watermilfoil from eastern Washington had significantly greater body length than those reared on Eurasian watermilfoil from western Washington. Results indicate that developmental performance on Eurasian watermilfoil is not always better than on northern watermilfoil, and performance may vary with watermilfoil population and/or host plant quality.