Confirming his decision to bow out of Test rugby, the 32-year-old said: "I'd like to thank the Irish management and particularly the players for their support during my 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.
"But after eight years in the squad I now feel this is the time to step down. 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."
Easterby is married to Sarra Elgan, the daughter of former Wales and British & Irish Lions winger Elgan Rees, and the couple have a one-year-old daughter Soffia.
The tough-tackling flanker has been a pivotal member of the Irish pack in recent seasons - playing in every game of the 2004, 2005, 2006 and 2007 Six Nations campaigns - and when both Brian O'Driscoll and Paul O'Connell were injured, he stepped in to captain his country against New Zealand and Australia in the 2005 autumn internationals.
An excellent tail-of-the-lineout jumper, he was one of five players in the Ireland set-up to make his Test debut against Scotland back in February 2000. He is now to concentrate on improving the fortunes of the Llanelli Scarlets, whom he has played for since 2003.
Easterby, Llanelli's long-time captain, added: "Over the next two years my main focus is on the Scarlets, where hopefully we can bring some success to the fans."
The 2005 Lion - he was called up as an injury replacement for Lawrence Dallaglio in New Zealand - has two more years to run on his current Scarlets contract.
He will be back facing some of his Ireland team-mates when Llanelli hosts Magners League leaders Leinster at Stradey Park on Saturday week.
SIMON EASTERBY PROFILE:
? 27.01.75, 6-3, 16-10
? Debut: 2000 v Scotland
? Overtook Anthony Foley (62 caps) as Ireland's most capped back row forward (v Italy, 2008)
? All 4 2007 World Cup games as a starter - try in the opener v Namibia
? Played in all 2006 and 2007 Six Nations games but then rested for both subsequent summer tours
? Captain in two 2005 autumn Tests v New Zealand and Australia, took over captaincy from the injured Brian O'Driscoll
? Won 20 caps in a row before missing Japan summer tour 2005, as he went on Lions tour, played impressively in last 2 Tests v New Zealand, scored try in 2nd Lions Test, then returned to captain country
? With the Llanelli Scarlets in Wales since their inception in 2003
? Played for hometown Harrogate, then Leeds Tykes and was eligible for England, but then had a spell with Sydney University before joining Llanelli in 1999
? Originally played for the Irish Exiles in early part of career and is younger brother of former Leinster scrum half Guy Easterby (28 Ireland caps, 2000 to 2005)
? One of the players who made their Test debuts v Scotland in 2000 immediately after the 50-18 loss to England