Robertson will be the only Canadian representative when he joins roughly 30 other local leaders from Europe, Africa, Asia and the Americas for a two-day conference with Pope Francis on July 21.
He received his invitation from the Vatican out of the blue as he didn't file any application, he told On the Coast host Stephen Quinn.
"It's a great honour. I'm looking forward to the experience of it. Obviously, it's a rare occasion to have that kind of access and to see a Pope in action."
Climate change a moral issue
"This is a key issue for the Pope — connecting the dots between climate, poverty, the existing slave trade around the world," Robertson said.
"The world's most vulnerable people are most adversely impacted by climate change right now, and that's what Pope Francis is focusing a lot of his energy on."
"It's great to see the Pope weigh in on this and actually make it a moral issue. It's stirred up a lot of debate and some controversy, which is I think a healthy thing in this case."
"We are noticed around the world as a city that is a leader on climate change," Robertson said, referencing Vancouver's commitment to become the world's greenest city by 2020 and to transition toward 100 per cent renewable energy sources.
"Around the world, people are seeing us as leaders and want to know what we're doing and how we're doing it."
However, Robertson expressed his dismay at the recent failed transportation plebiscite.
"That's a consequence where we're not walking our talk right now, unfortunately. I don't know if people connected all those dots when they were thinking about which way they voted."
Federal pressure needed
While this conference focuses on municipal leaders, Robertson hopes that the Pope will extend an invitation to Prime Minister Stephen Harper in the lead up to the United Nations' Climate Summit in Paris this December.
Robertson said Canada cannot "continue to embrace fossil fuels as the be all and end all of our national energy strategy."
"We're actually taking action and putting commitments forward proactively and pushing on national governments to ensure that they make binding significant commitments in Paris, but it is the national governments that will set the pace there."
To hear the full interview with Gregor Robertson, listen to the audio labelled: Gregor Robertson to meet Pope Francis.