Originally intended as a military route to connect the shipping port of York (now Toronto) to the envisioned future capital of London, Ontario, the street today connects Toronto landmarks such as Yonge–Dundas Square and the city's principal Chinatown to rural villages and the regional centres of Hamilton and London.

Dundas Street is also one of the few east-west routes to run uninterrupted through the central and western Greater Toronto Area, from Toronto to Hamilton (the others are Lake Shore Boulevard/Lakeshore Road, Eglinton Avenue, Steeles Avenue/Taunton Road, Queen Street (Brampton)/Highway 7, and Bovaird Drive/Castlemore Road/Rutherford Road/Carrville Road/16th Avenue).

At Yonge Street, Dundas passes Yonge-Dundas Square, within sight of downtown landmarks such as the Eaton Centre and Toronto Metropolitan University.

Designated Dundas Street West from this point westward, the route passes to the north of City Hall and Nathan Phillips Square.

Proceeding due west from Keele through the Junction, Dundas parallels the CP Rail line through the mixed industrial-residential district.

At Scarlett Road, the route veers southwest toward a high crossing over the Humber River valley, through the former village of Lambton Mills.

This route traverses the west end of the city, avoiding obstacles that were expensive to negotiate in the 18th century, such as Grenadier Pond in what is now High Park and the highest point of the Humber Valley (Bloor Street to the south requires a high bridge to cross the river at that point).

[3] From Kipling, Dundas is a six-lane arterial road, and began to follow the former Highway 5 (which ran along the more direct Bloor east of that point).

Upon crossing the Toronto boundary at Etobicoke Creek, the street enters Mississauga, in the Peel Region and follows a southwestern heading.

Immigrant communities have sprung up along the route of Dundas Street within Toronto, with most still retaining elements of their original character.

The Junction attracted many immigrant labourers from Ireland, Britain, and Southern and Eastern Europe due to its proximity to railways and heavy industry, such as meatpacking, which sprouted up there in the late 19th century.

The Dundas and Bay Street area, west to University Avenue, has been developing into a Little Tokyo district.

The section of the street near Dundas Valley, today known as Governors Road and earlier as Governor's Road, was surveyed by Augustus Jones and constructed by the Queen's Rangers from 1793 to 1794 as a military supply route at the direction of John Graves Simcoe, first lieutenant-governor of Upper Canada.

[12] The road was constructed away from the lake shore, and the American border, so a communication link could be maintained in the event of an invasion.

Montgomery's Inn was built on Dundas Street in 1830 for travellers along this route and also became a center of neighbourhood business in the village of Islington.

In the 1950s, the city of Toronto implemented a project to extend Dundas eastwards from Broadview to Kingston Road as a new four-lane traffic arterial in order to provide an alternative east–west route to Gerrard and Queen.

It is planned to run from Kipling Bus Terminal, which connects to Line 2 Bloor–Danforth in Etobicoke, Toronto to Highway 6 in Waterdown, Hamilton.

[28] Amid the protests following the murder of George Floyd in 2020, over 10,000 people signed a petition calling for the city to rename Dundas Street, due to Henry Dundas's "involvement in supporting the gradual abolition of the slave trade in the British Empire in the 18th century" as opposed to immediate abolition.

[29][30][31] On June 10, 2020, Mayor John Tory stated that a working group would be formed "to examine the issue of renaming streets in a broader sense".

[1][32] The city's process also sparked reviews of the use of the Dundas name in other areas of the province, including Mississauga, London and Hamilton.

[32][2] On July 6, 2021, the City of Toronto's executive committee unanimously supported the renaming of Dundas Street.

[33] During public deputations, former Governor General Adrienne Clarkson stated that "the name of Dundas has no relevance to Canada ... he has no connection to Toronto".