Speaking about the appointments, Lam said: "I'm delighted to confirm Gavin, John and Michael as club captains for the new season. We announced the captaincy to the entire squad today and the decision went down extremely well.
"In the professional era of rugby, when you have players joining your team from around the world and outside the province, it's important for everyone to understand the values of a Connacht player.
"Our own team identified those values as 'committed, tough, a team man, respected, and accountable.'
"These three men exemplify what Connacht Rugby is all about and they are fantastic ambassadors for the province. John and Gavin are both born and bred in Galway and Mayo, and Michael is the longest-serving player with a record number of caps.
"They care passionately about Connacht Rugby. They've seen where we have come from, they know where we are now and they want to be part of where we are going.
"They are all extremely committed and ambitions individuals and I know that they will continue to lead the squad with professionalism and passion.
"They act as a great support to the management team as well as the other players and there is a lot of respect there for them - both from within the province and from the supporters and the wider community."
Lam explained that the role of matchday captain would be shared amongst the trio as well as other members of the squad.
"Each week we will put out our best available team and will decide on the matchday captain to lead us on the pitch," he added.
"We have a larger leadership group working below the club captains which encourages players to take on more responsibility and allows us to build on the standards and progression of Connacht Rugby.
"There are a number of leaders here and I believe that we can all support each other very well over the coming season."
Duffy continues his duties for the third year as captain after a successful two seasons that saw him lead Connacht in their first ever Heineken Cup campaign during the 2011/12 season.
The 31-year-old full-back-cum-winger has been ever-present in the Connacht squad since his return to the province in 2007, following a four-year stint with Harlequins.
A former Mayo minor footballer who played in the 1999 All-Ireland MFC final against Down, he went on to become one of the select few to join the elite group of Connacht centurions by reaching 100 caps in 2010.
Galway man Muldoon joins Duffy in leading the squad for the 2013/14 season. The 31-year-old from Portumna has plenty of experience having captained Connacht for both the 2009/10 and 2010/11 campaigns.
In his first year as skipper, Muldoon led Connacht to victories over then Heineken Cup champions Leinster and Amlin Challenge Cup winners Cardiff Blues in the league, along with helping the side reach the semi-finals of te Challenge Cup where they lost narrowly to French outfit Toulon.
With three international caps to his name, Muldoon was most recently called up to the Ireland squad during last November's GUINNESS Series.
The back rower was unfortunately forced off with an injury during the second half of Ireland's non-cap international win over Fiji in Limerick.
With 198 Connacht appearances, Muldoon is just two games shy of joining his team-mate Swift in the 200-cap club.
In his fourteenth year with Connacht, club captain Swift continues to show his indisputable loyalty and commitment to the province.
The 6ft 5in London-born second row joined Connacht in 2000 and earned his first cap against Ulster that year whilst also playing for Galwegians in the All-Ireland league.
He became the first player in Connacht history to reach the 200th cap milestone when he lined out against Edinburgh in September 2011.
At the end of last season, 'Swift' was presented with the prestigious Chairman's Award at the annual RaboDirect PRO12 Awards.
The league's Chairman Andy Irvine recognised Swift for 'his outstanding service to both his province and the tournament as a whole'.
He became the first player to break the 150-match barrier in the league last season and has played in every one of the 12 seasons of Celtic rugby. Swift has signed on for at least one more season with Connacht.
Lam's men concluded their pre-season schedule over the weekend with the third friendly fixture against Newcastle Falcons, the head coach's former English club winning 23-10 at Kingston Park.
The westerners' squad will now have two weeks training before the first game of the RaboDirect PRO12 - Italian side Zebre will be the first visitors to the Sportsground on Saturday, September 7 (kick-off 5pm).