The All-NBA guard will have a player option for $52 million in the last year of the extension, sources said.
Lillard, 28, has two years and around $61 million left on his current deal. The extension would keep him in Portland through the 2024-25 season.
The extension was first reported by The Athletic.
The Weber State product, drafted No. 6 overall by Portland in the 2012 NBA draft, has helped lead the Blazers to the playoffs six times –most recently to the Western Conference finals, where they were swept by the Golden State Warriors.
In the first round, Lillard hit a series-clinching 3-pointer at the buzzer to eliminate the Oklahoma City Thunder in five games — the second series-clinching buzzer-beater of his career (2014 vs. Houston).
His 12,909 career points rank second in Blazers franchise history, trailing only Hall of Famer Clyde Drexler (18,040).