"McCollum became eligible for the extension on Saturday and joins All-NBA teammate Damian Lillard in landing summer deals that solidify the Blazers' backcourt into the mid-2020s," ESPN's Adrian Wojnarowski wrote.
McCollum's new deal will extend his contract to a total of five years and $157 million.
He is a native of Canton, Ohio, and after a shaky start to his pro career, has paired with Lillard to form one of the league's most formidable backcourts. The Blazers advanced to the Western Conference finals last season.
McCollum, 27, was the No. 10 overall draft pick in 2013. He was named the NBA's Most Improved Player in 2016.
He averaged 21.0 points and tied his career-high with 4.0 rebounds in 71 games last season. The GlenOak High product increased his scoring average to 24.7 points in the playoffs.
The Blazers signed Lillard to a four-year extension worth $196 million earlier this summer.