Trimble joins a growing list of international contracts being awarded, with Ronan O'Gara, Donncha O'Callaghan and Cian Healy also recently signing new Ireland deals.
Trimble made his Ulster debut in September 2005 against the Cardiff Blues and has so far played 111 times for his province.
He quickly followed that debut with his first international appearance for Ireland against Australia in November of that year and has so far won 31 caps and scored eight Test tries.
Commenting on the news, Trimble said: "Ulster and Irish rugby are going from strength to strength and my decision to stay in Ireland was to make sure I was part of that.
"We have some big games coming up, so I am really happy that I was able to agree my new contract before we went into the busy period.
"As well as the challenges we have in the Heineken Cup and Magners League coming up, I was conscious that I also wanted to concentrate on playing as well as possible here with Ulster so I can challenge for a place with Ireland ahead of the Six Nations and the World Cup this year.
"Our game this weekend against Biarritz is my first priority and everybody in Ulster Rugby is firmly focused on that."
Ireland head coach Declan Kidney said: "It is great news that the IRFU and Andrew have come to an agreement that allows him to continue his playing career in Ireland with Ulster.
"It is important for both the provinces and Ireland to keep as many of our top players playing here."
Ulster's operations director David Humphreys added: "Here at Ulster Rugby we're delighted that Andrew has chosen to continue and further his rugby career in Ireland.
"He's enjoying a rich vein of form, and as one of the senior members of the Ulster squad he's played an integral part in the improvements we've made this season.
"As we saw from his performance last weekend against Treviso, he's certainly back to his best."
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