"I've learnt so much about the NRL in my three seasons with the Roosters, adding to past experience with England and Bradford," he said.
"Now I'm really excited about this next step in my coaching career, coming to Auckland and working with Stephen and a great coaching group.
"I am in no doubt that the Warriors have the players to make a mark in the NRL and I want to do all I can to help make that happen.
"I have the greatest admiration for Stephen from the days when we were opposing coaches of our national teams. He has done wonderfully well with the Kiwis and I'm sure he's going to do a terrific job with the Warriors."
Kearney said he couldn't be happier to secure McNamara.
"While Steve and I were adversaries in our roles with our national teams we formed a great relationship," he said.
"He brings qualities that will give us a really strong and experienced coaching group as we look ahead to take the Warriors to the level we collectively expect of this club.
"There's much work to do but with Steve, Cappy and Stacey we have a coaching team that can really lift standards and bring about the improvements we must make to be consistently competitive in the NRL."
McNamara played more than 300 top-level games for Great Britain, Hull FC, Bradford, Wakefield and Huddersfield from 1989-2003 before moving into coaching including six seasons as England head coach.
Coaching Career
Club:
Bradford head coach, 2006-2010
Sydney Roosters assistant coach, 2014-2016
International:
Great Britain assistant coach, 2007
England assistant coach, 2008-2009
England head coach, 2010-2015
Playing Career
Position: Second row, loose forward
Junior Club: Skirlaugh, Hull
Club Career: Hull FC, 1989-1996
Bradford, 1996-2000
Wakefield, 2000
Huddersfield, 2001-2003
International Career: Great Britain, 1992-1999
