The SKC duo, who featured for the USA at the 2014 World Cup, signed multi-year deals with the defending MLS Cup champions which makes them Designated Players and locks them down through the 2018 World Cup.
"This is a dream come to true to know that I'll be playing my whole career in Kansas City," Besler said in a club statement.
"I have always respected players who have played their entire career with one team," Zusi said in the same statement. "And I look forward to a long career in Kansas City."
Zusi and Besler were both drafted in 2009 and they've since played over 130 matches each, playing major roles in Sporting KC winning their second MLS Cup title last year.
Besler, voted the 2012 MLS Defender of the Year, had a special connection to the club, growing up just a few miles away from Sporting Park.
"For me the ownership group showed commitment to both me and Graham," Besler told ESPN2 during halftime of Saturday's Seattle Sounders vs. Tottenham Hotspur friendly. "They've been doing it through our entire career and they basically made both of us an offer that we couldn't pass up, locking us down for a very, very long time and to have that security feels great as a player and we're certainly excited to keep pushing our team to the next level."
Besler and Zusi, who were both voted by the fans to the 2014 AT&T MLS All-Star Game vs. Bayern Munich, are the latest Americans to join the list of 38 Designated Players in Major League Soccer. Nine of those 38 players are USMNT members.
"For me it was a pretty easy decision," Zusi told ESPN2. "Kansas City and this ownership group have proven that they know what they're doing and we're certainiy headed in the right direction. We have the best fans and ownership group in the league and I think the league has reached a great level and in the near future there's a lot of exciting things coming up."