St. Elizabeth CHS was founded by the York Catholic District School Board in 1987, celebrating its 20th anniversary in 2007.

In the beginning, St. Elizabeth consisted of (and was only open to) grade nine students.

Due to the overpopulation of school enrolment, a change of site was announced and the current location began construction in 1988.

Once completed in January 1990, it was officially opened to students and staff in February 1990.

The high school's original location (at 21 Mullen Drive in Thornhill) was changed to Holy Family Catholic School, and officially opened in September 1990.