It is named for and directly connects to the railway station and regional bus terminal of the same name, serving all GO Transit train lines and train-bus services as well as Via Rail intercity routes (including Amtrak's Maple Leaf service to New York City).

In 2007, Union subway station became the first location on the TTC where Presto cards could be used, as part of a trial.

[3] The station opened as the southern terminus of the original Yonge subway line on March 30, 1954.

A new underground streetcar platform was built south of the subway tracks, connected to the station concourse by a 30-metre pedestrian tunnel and a flight of stairs.

The project also included an expansion of the concourse level, the replacement of all finishes and signage, installation of public art, as well as improved connections to the adjacent Union Station and the PATH network.

It features the art piece "Zones of Immersion" by Stuart Reid, a professor at the OCAD University[11][12] The work comprises 166 large glass panels, each measuring more than one by two metres, extending 170-metre (560 ft) along the length of the platform.

Public reaction towards the art piece has been mixed, with some users of the station finding it "tragic" or "dark and depressing".

North side entrances: South side entrances: Union Station Loop is located underground at the north end of a 500 m (1,600 ft) tunnel running under Bay Street through the underground Queens Quay station from the street Queens Quay.

[17] A 2017 TTC report stated that the streetcar loop would become inadequate for the volume of customers it handled because of its single track and its curved, narrow platform.

In 2017, conversion of the tunnel under Bay Street to operate a funicular shuttle to Queens Quay station instead of streetcars was considered but ultimately rejected.

[18] Nearby landmarks include the Union Station railway station, the Royal York Hotel, Scotiabank Arena, CIBC Square, Rogers Centre, the Metro Toronto Convention Centre, the CN Tower, Royal Bank Plaza, Brookfield Place, the Hockey Hall of Fame, and the Meridian Hall.