From here to just south of Finch Avenue, the freeway follows the boundary line between Toronto and Mississauga. It encounters the third multi-level junction along its length, with Highway 409, which provides access to the airport as well as the southbound to eastbound movement that cannot be performed at the interchange with Highway 401 to the south. Highway 427 continues straight north and narrows again to six lanes. After crossing the Kitchener GO line, it passes west of Woodbine Racetrack and beneath Rexdale Boulevard, Morning Star Drive, and Finch Avenue. The freeway bends slightly eastward, diverging from the Mississauga–Toronto boundary, and crosses the West Humber River where it drains from Claireville Reservoir. The highway crosses Steeles Avenue and enters Vaughan, as it approaches a fourth and final sprawling interchange with Highway 407. The freeway then passes through an undeveloped area before ending at a partial interchange with Highway 7.