The land on which Allan Gardens conservatory and park sits was donated to the Horticultural Society of Toronto to be used as free, publicly accessible space donated to plant display in 1958 by George Allan a local politician and landowner. In 1879, the horticultural society opened the horticultural pavilion and conservatory on the site which was used to host events and flower shows. The building was destroyed by fire in 1902.
In 1910, a new classically proportioned palm house conservatory building, designed by Robert McCallum, opened and is the central heritage feature on the site today. The conservatory has been expanded – once in 1920 and once in 1957 with the four show house wings.
In 2004 the University of Toronto donated the final Conservatory building, originally built in 1932. This building is used for teaching and programming by the Friends of Allan Gardens.