Jennings, made his debut for Leinster in 2001 away to Swansea, was educated in St. Mary's College Rathmines and will link up with his home province next summer after a successful two year spell with the Leicester Tigers.
In all, Shane made 43 appearances for Leinster over four seasons (including 10 in the Heineken Cup) before moving to England in the summer of 2005 and to date has made 35 appearances in all competitions (8 in the Heineken Cup) for the Tigers, scoring 9 tries.
He has also represented Ireland at Schools, Under-19, Under-21 and at 'A' levels and captained the Ireland 'A' side on the 2006 Churchill Cup competition in North America.
Leinster Chief Executive Mick Dawson commented: We are delighted to announce that Shane has re-signed with the province. Shane is an accomplished forward who will add greater competition to the Leinster backrow.
He has shown outstanding leadership qualities throughout his career and we look forward to welcoming him home to Dublin next summer.