Nowitzki moved by Garnett for 14th on the list after making a free throw with 3:03 remaining in the first half of the Dallas Mavericks' game Monday night against the Denver Nuggets.
Garnett, a 19-year veteran in his first season with the Brooklyn Nets, has 25,352 career points.
Nowitzki, who has spent all 16 of his NBA seasons with the Mavs, entered the night trailing Garnett by nine points.
It's possible that Nowitzki and Garnett could trade places on the all-time scoring list again Tuesday night, when the Nets have a road game against the Toronto Raptors. The Mavs' next game is at home Wednesday night against the Golden State Warriors.
However, it's likely that Nowitzki will create some distance between himself and Garnett on the all-time scoring list throughout the course of the season. Nowitzki was averaging 20.9 points per game this season before Monday night. Garnett is averaging a career-low 6.5 points per game with the Nets.
Kobe Bryant, who ranks fourth all-time with 31,617 points, is the only active player higher on the scoring list than Nowitzki and Garnett.
Alex English (25,613 points) would be the next retired player bumped down a spot by Nowitzki, who has already passed Jerry West and Reggie Miller this season.