Chris Cotillo of MLB Daily Dish reported that Wong will make $25.5 million over the five years.
The contract, which begins in 2016, guarantees Wong $1.25 million this year, $2.5 million in 2017, $4 million in 2018, $6.5 million in 2019, and $10.25 million in 2020, according to Cotillo.
The deal also includes a $12.5 million option for 2021 with a $1 million buyout.
Wong was not projected to hit arbitration until 2017 and was not scheduled to become a free agent until after the 2019 season. Now, St. Louis gains control over a cornerstone for two more seasons.
The 25-year-old was the Cardinals' 1st round pick (No. 22 overall) in the 2011 MLB Draft.
He had his first full season in the Major Leagues in 2014 and finished third in the National League Rookie of the Year voting. A defensive-first player, Wong was worth 1.9 FanGraphs Wins Above Replacement (fWAR).
In 2015, Wong hit .262/.321/.386 with 11 home runs and 61 RBIs in 613 plate appearances. Wong's overall play was better this past season, as he was worth 2.3 fWAR.
The 2015-2016 offseason was fairly quiet on the extension front, with Dee Gordon, Brandon Crawford, and Salvador Perez representing the only three players to receive extensions from their respective teams as of this writing.