The calculated distance (air line) between Niagara-on-the-Lake and Mississauga is approximately 36 miles respectively 59 kilometers.
By car or train, the actual journey to Mississauga is certainly longer, as only the direct route (as the crow flies) between Niagara-on-the-Lake and Mississauga has been calculated here.
Air line (approximately)
59 kilometers
32 nautical miles