Molinari was elected to the Ontario legislature in the provincial election of 1999, defeating Liberal candidate Dan Ronen in the riding of Thornhill. Molinari's bid for election was almost derailed early in the campaign when one of her pollsters asked constituents how they felt about being represented by a candidate who was the son of a Holocaust survivor (Ronen's father had survived internment at Auschwitz, and Thornhill has a large Orthodox Jewish population). She overcame this controversy, however, and defeated Ronen by 343 votes.