Retallick said his ambition to play in back-to-back Rugby World Cups was a big motivator to remain in New Zealand.
"I am only young and still have plenty to learn about the game," he said. "There is a lot I want to achieve and I firmly believe that New Zealand is the best place for me to grow my game and accomplish my goals. I have access to the best coaches in the world, play in teams with great lads and great environments and am really enjoying my footy."
Savea said the decision to re-sign was, ultimately, an easy one to make.
"There are still a lot of things I want to achieve in New Zealand rugby and I love playing for both the Hurricanes and the All Blacks, love the jerseys, want to continue to grow as a player and help both teams succeed and add to the legacy.
"I love the environment in both teams and the fact that a bunch of Hurricanes boys play for the All Blacks as well just makes it even better. We just want to play well for the team, for ourselves and for our fans."
Retallick and Savea are the first players to re-sign with NZR and their respective Super Rugby clubs through to the end of the 2019 season.
"This is a very significant announcement for New Zealand Rugby," NZR chief executive Steve Tew said. "Brodie and Julian represent a big part of the future for us and we are delighted to have them sign for four more years.
"We know our players have choices, so to have them commit long-term to New Zealand Rugby is very pleasing, and I want to thank them both for their commitment to New Zealand.
"It's an exciting period for rugby in this country and they will now be part of some very important events, including the revamped Super Rugby competition from next year, the British and Irish Lions Tour in 2017 and Rugby World Cup 2019."
Tew also said that, as with other long-term contracted players, NZR and the players' representatives had agreed terms which would ensure the players' workloads were managed appropriately, but added that there were no extended breaks to play overseas or long-service leave in the contracts.
Savea and Retallick join a raft of current All Blacks who have re-signed beyond this year, including Jerome Kaino (2018), Kieran Read, Owen Franks, Sam Whitelock, Cory Jane, Israel Dagg, Aaron Cruden, Ben Smith, Charlie Faumuina, Steven Luatua and Malakai Fekitoa (2017) and Dane Coles, Sonny Bill Williams, Aaron Smith, Beauden Barrett, Luke Romano, TJ Perenara, Dominic Bird and Patrick Tuipulotu (2016).