Warren's agent, Ty Sullivan of CAA Sports, and Suns general manager Ryan McDonough completed talks on the deal Monday afternoon, sources said.
Warren, 24, is part of the 2014 NBA draft class eligible for its rookie extension.
For Warren, the agreement represents long-term financial security based on several factors, including his run of injuries as a pro and what appears to be shaping up to be a treacherous market devoid of salary-cap space for restricted free agents next summer.
Warren has missed portions of his three NBA seasons with injuries, including season-ending foot surgery in 2015-16.
For the Suns, the deal secures one of the franchise's stable of talented young cornerstone players.
Warren has shown tremendous potential as a versatile wing with significant scoring potential. He had his best -- and healthiest -- pro season in 2016-17, averaging 14.4 points and 5.1 rebounds while starting 59 of his 66 games played.
The Suns didn't agree on a rookie contract extension with center Alex Len, the fifth pick in the 2013 draft, who signed a qualifying offer for the 2017-18 season and will become an unrestricted free agent in July.
Warren was the 14th overall pick out of NC State in the 2014 draft. He left for the NBA after two college seasons, earning ACC Player of the Year and second-team All-American honors in 2013-14.