The 28-year-old full-back has become an integral part of the Ireland set up since making his interational debut against Argentina in June 2005.
Kearney has scored 10 tries in 56 caps with Ireland, while he was selected for the British and Irish Lions tours of South Africa and Australia in 2009 and 2013 respectively.
Domestically Kearney won the Heineken Cup on three occasions with Leinster, as well as an Amlin Challenge Cup and three Pro12 titles.
"I am happy to have signed a new contract that will keep me at Leinster for another three years," he told the IRFU's official website.
"I made my debut for Leinster almost 10 years ago and it is a great honour be in a position to extend my contract and hopefully play a part in future success at both provincial and national level."
Leinster chief executive Mick Dawson added: "It is great that Rob has signed a new IRFU contract which keeps him at Leinster up to the end of the 2018 season.
"Rob is a senior international with a proven pedigree and a key voice within our environment.
"Keeping our stars at Leinster will ensure that we continue to compete for silverware in our domestic competition and in Europe."