The deal will see Kearney, 46, remain in the role for six seasons, joining Ivan Cleary (2006-2011) as the longest-serving head coach in the club's history.
"Securing Stephen for another three years is a huge boost for us," Warriors chief executive Cameron George said.
"We haven't enjoyed a lot of stability as an organisation, especially in the coaching area. Without stability in our football department it's extremely challenging to improve and to achieve continuity," he said.
"We've been talking with Stephen for some time about ensuring he remains to continue the work that has been going on and we couldn't be more pleased he's staying on for another three years," said George.
After four seasons as an Auckland Warriors player from 1995-1998, Kearney is now on track to take his connection with the club to a total of 10 seasons with his new contract.
"When I first came back to the club, I was honoured to be given the opportunity to help the club move forward and improve," he said.
"I'm pleased to have my future sorted out with this new contract and to know I'll be with the club for a few more years.
"We made progress last season but, to be honest, the focus for me is always what's next for us and that's preparing for this week's trial against Wests Tigers in Whangarei."
The Vodafone Warriors' season-opening match against the Bulldogs on 16 March will be Kearney's 50th as the club's head coach and his 92nd overall.
After finishing his playing career in 2005, Kearney moved straight into coaching, starting with five seasons as an assistant coach with Melbourne as well as launching a nine-year term as Kiwis coach in 2008.
During that time, he guided the Kiwis to three major titles - the World Cup in 2008 and the Four Nations in 2010 and 2014.
Warriors head coach 2017-2019
New Zealand Kiwis head coach 2008-2016
Brisbane Broncos assistant coach 2013-2016
Parramatta Eels head coach 2011-2012
Melbourne Storm assistant coach 2006-2010
International: 45 Tests for Kiwis 1993-2004
NRL: 264 first-grade appearances 1992-2004
Western Suburbs: 46 appearances 1992-1994
Warriors: 79 appearances 1995-1998
Melbourne Storm: 139 appearances 1999-2004
46 appearances for Hull FC 2005