The most capped Ireland back-row said will now focus on his playing career with the Welsh region.
"With the demands on international rugby players these days, and with a young family, I feel this is the right time to move on to the next stage of my life and over the next two years my main focus is on the Scarlets, where hopefully we can bring some success to the fans, he said.
Easterby won his first international cap against Scotland in 2000 and has subsequently scored 40 points wearing the green of Ireland. The 32 year old former British and Irish Lion has featured in every Six Nations championship between 2004 and 2007 and captained Ireland during 2005 Autumn series. Speaking about his international retirement, the Scarlets player felt very fortunate to have played with some of the great players and expressed his thanks to those who supported him throughout his international career.
"I've been extremely fortunate to play with some of the great players of Irish rugby and it has been a privilege to be involved with them and I've enjoyed every minute of it."
The forward still has a further two years to run with Llanelli Scarlets and has already played 47 times in Heineken Cup for the Welsh region.