Kevin Durant had 36 points and 10 rebounds as the Thunder evened the series against the Blazers 2-2 in their final regular-season meeting this year.
Jeremy Lamb had 19 points, including a key 3-pointer with 1:38 left for the Western Conference-leading Thunder, who have won 14 of their last 16 games.
Nicolas Batum had 18 points for slumping Portland, which has lost five of seven but still ranks third in the conference behind San Antonio. Robin Lopez finished with 17 points and 14 rebounds for his 19th double-double of the season.