The two prime ministers laid wreaths at the memorial and they also interacted with a group of people who had lost their kin in the crash, Canada's worst terror incident.
Modi, along with Harper, visited the Kanishka memorial site in Humber Bay Park as his final stop in Toronto before heading west to Vancouver.
The Montreal-New Delhi Air India 'Kanishka' Flight 182 exploded 45 minutes before it was to have landed at London's Heathrow Airport on June 23, 1985, killing all 329 people on board, most of them Canadians of Indian descent.
Inderjit Singh Reyat is the lone man convicted in the Kanishka bombing case.
The memorial was unveiled in 2007.
