Weston Collegiate Institute is the second-oldest secondary school in Toronto and the oldest in the former City of York, having been established in 1857 as Weston Grammar School. The school's activities and scholarships are supported by the Weston's Alumni Foundation. The school was renamed to Weston High School in 1871, then Weston High and Vocational School in 1922, and lastly to Weston Collegiate and Vocational School in 1939 before adopting its present name in 1965.

WCI displays an international focus as the student body representing over 80 countries in the world.

The original school building on King Street was built in 1858 and was replaced in January 1876 after a fire burned the original school on March 23, 1875. The enlarged school, designed by architect Stephen Burwell Coon, was built in 1913 facing William Street with six classrooms, an office, a science lab and an gymnatorium. In 1952-53, the building gained additional features such as more classrooms, auditorium, cafeteria, library, gymnasium, offices and music room. The school's modern facility was constructed in 1968 in the old track and field and was opened in September 1970. The brutalist building includes a library, auditorium, a large indoor pool, a full-sized field with surrounding track, a double gymnasium and a fitness/weight room.