The Munster and Ireland scrumhalf had been offered an IRFU contract, but instead opted to play his professional trade across the water with the all-conquering Tigers.
Since coming back from a serious injury towards the end of this year's AIL season, Tierney has been overtaken in the pecking order as number two to Peter Stringer. He also faced strong competition from Mike Prendergast of Young Munster and Shannon's Derek Hegarty in contention for this much sought after position in Munster.
Dean Richards, Director of Rugby at Leicester, is said to have originally set his sights on Stringer but hopes of that deal materialising faded. Now Tierney is set to resurrect his career alongside fellow Irishman Geordan Murphy at Welford Road.
Prior to yesterday's announcement Garryowen Honorary Secretary, John Griffin, the club stated that they felt it would be a good move for Tom. "The rumor is that he passed all tests and he is going to be offered something from them. If he leaves, we wish him the best."
Tierney's, eight caps were all won successively at number 9 for Ireland between 1999-2000 including the whole of the 1999 Rugby World Cup until sidelined with a shoulder injury.
He played his club rugby for Garryowen in Limerick, and has skippered Ireland A, but an injury prevented him from playing for Munster against Tigers in the Heineken Cup final earlier this year.
Tierney is not the only new signing at Leicester, and yesterdays announcement also saw the unveiling of two other new signings. French tighthead prop Franck Tournaire, and top Welsh prospect, hooker Rhys Williams, have also just been added to Leicesters books as they enter the season with the aim of defending their Zurich Premiership and Heineken Cup crowns once more.
Following yesterday's announcement, Tierney stated "It's a huge opportunity for me to play with the best team in Europe. It was very difficult to leave Munster because I started my career there, but I felt that I needed a fresh start. With the World Cup coming up next October, I feel that if I can do well here I can hopefully push into the Irish squad."