Originally, St Leonards applied to the whole area from the present suburb of North Sydney to Gore Hill.

After World War II, St Leonards, which had been a largely residential and industrial area, began to change.

In the late 20th and early 21st centuries, St Leonards underwent a process of gentrification, as older homes were replaced by modern apartments and office buildings.

The area became more desirable to young professionals due to its proximity to the Central Business District (CBD) and the integration of mixed-use developments.

Until the 2010s, St Leonards contained one of Sydney's suburban skyscraper clusters, with major offices for large companies including CIMIC Group, IBM, Lenovo, Manchester Unity, Oporto, Savvytel, Toyota Australia, 2UE, and Channel 31.

The Forum is built over the railway station and comprises three commercial office buildings, two residential towers containing 782 apartments, an independent mini-supermarket, and 34 food and retail shops.

Bus services through St Leonards are operated by Busways, CDC NSW, Keolis Downer Northern Beaches, Transdev John Holland and Transit Systems.

The Northern Suburbs Rugby Club has its clubhouse in St Leonards, featuring the Cabana Bar and Lounge.