The Balbriggan man was capped for Ireland Youths, scored a try against the England Under-18s in 2005 and was part of the Ireland Under-20 squad, coached by Connacht's Eric Elwood and Dan McFarland, which won the Six Nations Grand Slam in 2007.
Now 23, the talented tighthead prop has been a cornerstone of the Connacht scrum for the past season-and-a-half and his commitment to Connacht for the next two years will see him remain at the Sportsground until 2013.
Hagan, who stand at 6ft 3in and weighs 120kg, said: "I've really enjoyed myself here at Connacht and I'm really looking forward to playing with the province for the next two seasons.
Connacht CEO Gerry Kelly said that this sign of commitment from such an integral member of the current squad was very encouraging, adding: "Jamie has really fitted into the Connacht set-up and to have him commit to the province for the next two seasons sends out a strong message."
Connacht head coach Eric Elwood was equally as pleased, stating: "We had followed Jamie's progress as a young player, and obviously his involvement in the Ireland Under-20 Grand Slam side proved his ability so we knew his pedigree.
"He has excelled here at Connacht and we are very pleased that he has shown his commitment by signing a new deal.
"Jamie is a huge part of our squad and we look forward to working with him over the coming months."