 Highway 405 begins by diverging from the QEW at St. Catharines. It continues north-east for 1.5 kilometres (0.93 mi), then gently curves south-easterly. The opposing lanes, initially separated by a wide gap, converge towards each other to form a 15-metre (49 ft) grass median. The highway dips into a shallow gully, widens to five lanes (three eastbound, two westbound), and then curves northeast to pass north of a hydroelectric reservoir. The opposing lanes converge, with an Ontario Tall Wall separating them, and pass beneath Niagara Regional Road 102 (Stanley Avenue). The freeway's lone interchange is with Stanley Avenue, and traffic continuing east must cross the Lewiston – Queenston Bridge into the United States. The additional eastbound lane provided along this section is for the queueing of trucks. After passing the reservoir, the highway reaches the Canadian border plaza. It then passes over the Niagara Parkway and heads onto the Lewiston – Queenston Bridge over the Niagara River. The Highway 405 designation ends at the border with the United States, where it continues as I-190 towards Buffalo, New York. As Highway 405 entirely lies within the Province of Ontario and is not subject to federal administration, its entire length is patrolled by the OPP.
