The Titanic star was en route to Moscow when an engine on the Delta aircraft shut down, forcing pilots to make an emergency landing at New York's JFK International Airport.
The actor refused to let the scary incident derail his plans to attend the summit and promptly chartered a private jet, which got him to St. Petersburg, via a refuelling stopover in Finland, on Tuesday (23Nov10).
And his bravery and dedication to the cause has earned him high praise from Putin.
Speaking at a charity concert at the summit, the politician said, "Not everyone would be willing to take a plane again after what Mr. DiCaprio experienced, but he did. Here, in Russia, we call such a person a 'real man'.
"If wildlife and tiger conservation is in the hands of people with such character, we are destined to succeed."
The meeting of the world's high powers is being held to discuss what can be done to save tigers from extinction in the 13 countries where the big cats currently live and breed in the wild.
On Tuesday (23Nov10), DiCaprio pledged to donate $1 million (£667,000) to the World Wildlife Fund on behalf of his environmental organisation, the Leonardo DiCaprio Foundation.
He said, "Illegal poaching of tigers for their parts and massive habitat loss due to palm oil, timber and paper production are driving this species to extinction. If we don't take action now, one of the most iconic animals on our planet could be gone in just a few decades. By saving tigers, we can also protect some of our last remaining ancient forests and improve the lives of indigenous communities."