Crowds - including six former Olympians from Northern Ireland - gathered at Titanic Belfast to see the pair, who each claimed bronze at the games.
Barnes became the first boxer from the country to win medals at successive Olympics and paid tribute to the fans for their support.
"The atmosphere during the fight was unreal," he said.
"It's great, I was over the moon to qualify but now I've created history to become the first [Irish] boxer ever to win two Olympic medals."
Barnes and Conlan waded through a crowd straining to get a glimpse of the stars, signing posters and cards, maintaining a sense of humour while looking tired after days of effort.
Barnes's father, Paddy, said: "They are just shattered."
Later, Michael Conlan brought his bronze medal to the Falls in west Belfast to celebrate his win with family and friends.
I've realised tonight that everyone's really proud of me.
"It's been unreal," said the 20-year-old fighter, who is a member of St John Bosco club.
"I didn't think there was going to be anyone at my house, but it's massive."
Michael's mother, Teresa Conlan said they were delighted with the support from the people in her community.
"It's the inspiration of the young children of the Falls, that we'll give them something to look forward to and try to emulate," she explained.
On Tuesday, the bronze medallists will parade through the city centre on an open-top bus, which will run from 1pm to 2pm, starting at Writers' Square in Cathedral Quarter, along Royal Avenue and down Donegall Place before passing around City Hall.
Meanwhile preparations are continuing for the return of Coleraine's Olympian rowers - silver medal winning brothers Peter and Richard Chambers, and single sculler Alan Campbell.
They will arrive home on Wednesday and will be greeted at Bann Rowing Club, where they are members, before walking into Coleraine for an outdoor celebration event.
Northern Ireland athletes claimed their largest ever medal haul in 2012.
It started when the Chambers brothers rowed their way to second place with Team GB in the men's lightweight four at Eton Dorney on Day 6 of the competition.
Campbell followed up a day later when he was roared across the line by supporters on his way to bronze in the men's single sculls.
There have been calls to erect a statue dedicated to the trio in the North Coast town.
Success in rowing was followed by success in boxing.
Barnes, who is 25, became the first Irish boxer to medal at two consecutive Olympics after he also won bronze in Beijing four years ago.
On both occasions he has lost out to eventual champion Zou Shiming of China.
Conlan, the 20-year-old Team Ireland teammate of Barnes, picked up bronze at his first Games after losing to Cuba's Robeisy Ramirez Carrazana, who went on to take gold.
Sports Minister Carál Ní Chuilín praised the efforts of local competitors.
"I applaud all local athletes across the whole range of sports," she said. "While we celebrate those who achieved medals, I commend everyone who took part in the Games.
"They have taken on the best in the world on the biggest stage and are truly an inspiration."