Thomas Street runs southwest-northeast from Ninth Line to Queen Street South, roughly halfway between Britannia Road and Erin Centre Boulevard, passing through Churchill Meadows, Castlebridge, Erin Meadows and Streetsville. Landmarks include Streetsville GO station, Thomas Street Middle School, Stephen Lewis Secondary School, St. Joan of Arc Secondary School, and two strip malls at Glen Erin Drive and Tenth Line.
Bus route 9 Rathburn-Thomas serves most of the street. There is a bike path between Tenth Line and Erin Mills Parkway. Street parking is allowed west of Winston Churchill Boulevard and east of the CPR tracks. Through Streetsville there is a unique traffic control system where loop detectors at unsignalled intersections influence nearby signals to keep queues from growing too long.
Thomas east of Winston Churchill is a given road following a Second Purchase lot line. As part of the construction of Erin Mills Parkway in the 1970s, the part between Erin Mills and Vista Boulevard was bypassed to the south on an alignment with a gentler grade and no frontage, leaving Turney Drive in its wake. West of Winston Churchill, the street is fully new construction, built together with development in the 2000s, and curves north around Tenth Line to avoid slicing a woodlot in half.