Paul Doyle, a Translink Metro driver based at the Falls Road depot, stopped in November to give the man a winter coat he had bought for him.
He received the special award from the National Campaign for Courtesy.
The charity described him as a true inspiration whose generosity had touched the hearts of the nation.
Mr Doyle's act of kindness was witnessed by passengers - one of whom posted to Translink's Facebook page.
The post was shared on Facebook by AnnaMarie McDaniel. She wrote: "Couldn't believe how kind the bus driver was, such a thoughtful act".
The post was seen by more than 65,000 people and was shared more than 3,700 times.
Mr Doyle noticed the young man outside while out driving during his shifts and was concerned by his lack of suitable clothing in cold and often wet winter weather conditions.
He decided to buy the man a warm coat and give it to him the next time he passed by in his bus.
Paul received a special certificate from Paul Smith, from National Campaign for Courtesy, who said: "I came across Paul's story while reading the 'Metro' newspaper on my daily commute through London - just as his act of kindness went viral.
"Paul is a true inspiration," he said.
"It shows how even one simple act of generosity can be so powerful it touches the hearts of an entire nation and raises the profile of a serious societal issue.
"Kindness has a knock-on effect. Paul tells me that both he and other Belfast bus drivers have observed that car drivers are more patient since this story went viral.
"On behalf of the National Campaign for Courtesy, I would like to thank Paul and officially recognize his exceptional thoughtfulness."
On receiving his award, Mr Doyle said: "It's brilliant - I'm pleased I've made more people think about people in need out there.
"I'm blown away by the reaction - my passengers are still talking about it."
A Belfast bus driver who stopped his bus to give a homeless man a winter coat has won a national award for his kindness.