The announcement ends speculation that Kearney could have been tempted overseas just as Welsh Lions James Hook and Lee Byrne have been in recent weeks.
Kearney, who won a brace of Test caps for the Lions two years ago, is currently recovering from a knee injury but he hopes to be back in action soon as Leinster chase Magners League and Heineken Cup glory.
"There is nothing like representing both Leinster and Ireland and a big deciding factor was our supporters and the fact I think there is a lot more success to come for Leinster and Ireland," said Kearney, who has played 27 times for his country.
"This allows me to concentrate on returning to full fitness as soon as possible and put myself into contention for selection for Leinster and Ireland.
"I have certainly missed playing over the last number of months but my injury is coming along and hopefully I will be back soon."
Kearney follows fellow high-profile Lions Brian O'Driscoll and Jamie Heaslip in extending his stay with Leinster and head coach Joe Schimdt believes the news is a positive step for both club and country.
"We're delighted that Rob has agreed a new deal with Leinster and Ireland and we look forward to welcoming him back to the fold over the coming weeks," said Schmidt.
"Rob has played an important role in the province's recent success and I know how proud he is to represent his home province. Today's announcement is another timely boost for Irish rugby."