The following are the primary OC Transpo routes serving Old Ottawa South seven days a week:
- #1 - Runs from the South Keys Shopping Centre near Hunt Club, up Bank Street to Wellington, and on to the Rideau Centre.
- #4 - Runs from Billings Bridge Shopping Centre, up Bronson Ave., along Chamberlain (or Catherine St. on the return trip; each is one-way) near the Voyageur Bus Terminal, to Bank St., north to Wellington, by the Rideau Centre, and loops through Lower Town, and into New Edinburgh.
- #5 - Runs from Billings Bridge Shopping Centre, along Riverdale Ave. to Main St., downtown via Elgin, along Rideau St. (by the Rideau Centre and the Byward Market area), and then meanders east through Lower Town, Vanier, Ottawa East and south to the St. Laurent Shopping Centre.
- #7 - Runs from Carleton University (via Grove/Sunnyside) to Bank St., north to Rideau, past the Rideau Centre, and then east through Lower Town, and south along St. Laurent to the St. Laurent Shopping Centre.