St. Joseph's Oratory, managed by the Congregation of the Holy Cross, will see $80 million in upgrades and new installations in a five-year project set to begin in 2017.
The project includes a 360-degree observatory that will allow visitors to see as far as the American border 40 miles away.
Upcoming changes also include a new pavilion to welcome visitors, a redesigned garden, new outdoor lighting, installation of mechanical transports to help people climb the hill to reach the basilica and the restoration of the museum.
A spokesman for the congregation said the modifications will modernize the oratory founded by St. Andre Bessette, who was known as Brother Andre.
Founded in 1904 and built atop Mount Royal, the oratory welcomes 2 million pilgrims and visitors each year.
The project will be financed in part by the oratory, which will invest $26.4 million, including $10 million from the city of Montreal. The Canadian government will provide $22 million and the Quebec provincial government will provide $30.8 million .
"When this is done, we will offer a greener, more convivial, and more accessible site," said Holy Cross Father Claude Grou, oratory rector.
Father Grou recalled that original plans for the basilica included an observatory, and that pilgrims and visitors have been wishing for it for many years.
"This investment will allow us to add a very interesting dimension to this key-site in our cultural and historical heritage. In a way, (the observatory) will complete St. Brother Andre's dream," he added.
During a June 6 meeting to unveil the plan, Montreal Mayor Denis Coderre, stressed that the oratory is a symbol of the city. "Its shrine will be transformed and restored by works worthy of its notoriety and stature," he said.
Representatives of both the federal and provincial governments were on hand for the announcement. They said the funding is a gift to celebrate the 375th anniversary of Montreal's founding in 2017.
The work will occur in two phases. The first, from 2017 to 2019, will include all exterior work. The second, beginning in 2019, will see the construction of the observatory within the basilica's dome.