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.
"The set-up is very good here with all the facilities on-site and the coaches are very fair to work with - if you work hard, you are rewarded."
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."