Wong, 25, is a career .250 hitter who became one of the best-fielding second basemen in the National League last season. He is eligible for arbitration for the first time in November. The Cardinals are giving him the opportunity to take over their leadoff spot this spring, which would allow them to use Matt Carpenter in a more run-producing part of the order.
The contract, which will pay Wong $25.5 million, according to a source, also has a $12.5 million team option for 2021. It does not include any no-trade protection. Wong batted .262 with 11 home runs and 15 stolen bases last season.
"My whole plan was I wanted to be part of this team. I wanted to get engulfed with the community and just be part of St. Louis," Wong said. "Now, with this deal, I get to be part of the community."
Wong probably could have made more had he gone through the process of arbitration and free agency, but this gives him long-term security in case of an injury. Fellow Cardinals Adam Wainwright, Carpenter and Matt Holliday attended Wong's news conference. Carpenter agreed to a six-year, $52 million extension two springs ago at the same juncture in his career.
The Cardinals have made a habit of buying out arbitration seasons for homegrown players.
"He's a great example of our strategy to sign, develop and retain the best players available," Cardinals owner Bill DeWitt Jr. said. "As a first-rounder, he's certainly lived up to his billing."