The road has a long history and dates back to 1850s Toronto Nursery that was run by George Leslie.

Leslie was one of the first settlers in the area, at the time a community named Leslieville, located two miles east of the-then city limits of Toronto.

North of Danforth, the open concession resumed to end at the Don River Valley (near present-day O'Connor Drive), but that section is named Donlands Avenue today.

It exits Toronto and enters York Region at Steeles Avenue, west of Don Mills Road.

Leslie is reduced to a local road at Steeles Avenue and ends shortly thereafter in Wycliffe Park.