Tohn has been acting professionally since approximately age 9, but her first major role came on The Nanny at age 12. Jackie attended Camp Lokanda in Glen Spey, New York. She attended Oceanside High School in Nassau County, New York. After high school, she went to the University of Delaware for a semester and majored in elementary education and in the fall of 1998 was in an a cappella group called the Deltones. In November 1999, she starred in the one-act play "This Property is Condemned" by Tennessee Williams at the Chapel Street Theatre.