In 1929, the Council of the Township of York decided to construct a high school in memory of their youth killed in World War I and purchased 9.5 acres (3.8 ha). Architect Charles Wellington Smith designed the building and the cornerstone was laid on May 6. The school was opened on September 3, 1929, to its first students. The Collegiate Gothic building with Don Valley Brick and smooth faded stone, consists of 15 classrooms, 3 science labs, an auditorium, cafeteria, two gyms, a swimming pool, and various offices. It was built at a cost of $250 000.^[3][4] The school officially opened on January 30, 1930.

A World War II memorial was dedicated on February 27, 1949.^[5]

Since the building was originally constructed in 1929, in 1954, an addition with six classrooms was added.^[4] This is followed by the construction of seven classrooms and library in 1961, followed by fourteen classrooms and pool area conversion in 1966. The next year, in 1967, a new swimming pool was built in the site of the Centennial building, with a gym and community centre.^[4] Eight rooms were converted between 1968 and 1969.^[4] The last addition, in the eastern portion, was built in 1971, currently houses the cafeteria, library, and the offices of the York school board (which are currently used by the TDSB as its continuing education offices).^[4]

By 1973, fire escapes were added, space in the interior was converted for lockers. Some rooms were also converted in 1988.^[4]

In 1985, the building was designated as a heritage building by the York City Council.^[6]

On May 6 and 7, 2019, fires started in the YMCI building, which reached six-alarm status.^[7] The second fire caused sections of the roof and walls to collapse, as well as damage or destruction to the stained glass windows in the auditorium.^[8] All of the students were temporarily housed in nearby George Harvey Collegiate Institute.

The school is being rebuilt using materials including brick and a stained glass window salvaged from the remnants of the current building. TDSB is projecting the completion in 2026.^[9]

In December of 2022, 14 teachers refused to work citing unsafe working conditions.^[10] Students subsequently staged a walkout due to the teacher shortage and safety concerns.^[11]

York Memorial has Roadmap to University with Success with Honours (RUSH) and Advanced Placement (AP) programs. The RUSH program is an enrichment program that trains students for the full AP program. AP courses are offered in a wide variety of subjects.^{[citation needed]}

There is also a Pre-Advanced Placement program (10 English, 11 Biology, 11 Physics, 11 Chemistry) which students attend in grades 10 to 11 before taking the AP program in grade 12.

• Samantha Bee – Comedian, The Daily Show correspondent
• Dave Devall – Retired weatherman
• D-Sisive – rapper
• Harry Sinden – Former Boston Bruins' president
• Gail Kim – WWE Wrestler/diva and TNA Knockout
• Alan Tonks – Canadian former Liberal MP
• Ross Dowson - Trotskyist leader and political activist
• Chuck Crate - leader of the Canadian Union of Fascists

• List of high schools in Ontario

• Official website
• TDSB Profile
• "York Memorial Collegiate Institute School profile" (PDF). Toronto District School Board. Retrieved May 29, 2009.

• "York Memorial Collegiate Institute" (PDF). Tdsb.on.ca. Retrieved December 9, 2017.
• Computer studies at York Memorial
• CBC archives: Recording of Runnymede Collegiate Institute versus York Memorial Collegiate on the radio quiz show "I.Q.".
• Our Heritage
• York Memorial Collegiate Institute on TOBuilt