"The All Blacks and Crusaders have some exciting things coming up over the next few years and I'm really looking forward to being part of that. I love playing for both teams. The time is right to commit to New Zealand long-term, doing the right thing for my family played a big part and I'm incredibly happy with the decision.''
At 24, Whitelock has already amassed 47 test caps since making his debut in 2010 and quickly cemented his place as one of the starting locks in the All Blacks and Crusaders.
"Playing for both teams is a dream come true for me and I am really enjoying my rugby at the moment. I feel I am constantly learning and developing my game at the highest level and knowing that I will continue to do that in New Zealand over the next four years, playing alongside my mates, is an awesome feeling. There are some exciting times coming up for both teams,'' Whitelock said.
All Blacks head coach Steve Hansen said: "The fact that two world-class players in Kieran and Sam have re-signed for four more years is a huge positive for the All Blacks. Not only are they part of the current success of the team, but it means we have a nucleus of experienced players to take the team into the future beyond 2015, which is fantastic. It's also great news for All Blacks and Crusaders fans, knowing that both players have committed to New Zealand rugby in the long-term.''
Crusaders head coach Todd Blackadder added: "These are undoubtedly two of the best players in world rugby at the moment. More than that though, they are both inspirational, committed team men who bring so much to the Crusaders environment.''
Read and Whitelock have joined in-form All Blacks utility Ben Smith who has also signed through to end of the 2017 season.
A growing list of current and former All Blacks have also recommitted to New Zealand Rugby.
Contracted until 2016: Hooker Dane Coles.
2015: Captain Richie McCaw and fellow loose forwards Liam Messam, Sam Cane and Steven Luatua. Hooker Keven Mealamu, props Ben Franks, Wyatt Crockett and Ben Afeaki. Locks Brodie Retallick and Jeremy Thrush, halfback Tawera Kerr-Barlow, first-five-eighths Daniel Carter and Colin Slade, midfielder Francis Saili and outside backs Julian Savea and Charles Piutau.
2014: The All Blacks' most capped prop Tony Woodcock and fellow props Owen Franks and Charlie Faumuina. Hookers Hikawera Elliot and Corey Flynn, lock Luke Romano, loose forwards Victor Vito and Matt Todd. Halfbacks Piri Weepu, Aaron Smith and Andy Ellis, first-five-eighths Aaron Cruden and Beauden Barrett, midfielder Conrad Smith and outside backs Israel Dagg, Cory Jane and Zac Guildford.