Muldoon made his debut for Connacht in 2004. The talented second row has signed a new contract up to the conclusion of the 2011/12 season.
Kelly said: "It is great that John has committed his future to Connacht. He has been a great player and leader over the past few seasons, having come up through the ranks."
Muldoon, who made his 100th appearance for the province at the start of the season against the Ospreys, has played for Ireland at Youths, Under-19, Under-21 and 'A' levels.
"I am delighted to extend my contract with Connacht. We have made a lot of progress in recent years and I want to help build on that," the 26-year-old explained.
"At this stage, though, all attention is on Friday's game against Dax where we will hopefully secure a place in the quarter-finals of the European Challenge Cup."