Josh Smith and Mike Bibby added 24 points apiece for the Hawks, who won all four meetings with the Knicks this season, sweeping the series for the first time since moving to Atlanta for the 1968-69 season. Al Horford finished with 19 points and 11 rebounds.
The Hawks host Boston on Saturday in what could be a preview of a first-round series.
Atlanta was in control most of the way, though the Knicks cut what was a 21-point deficit to 96-91 on Quentin Richardson's 3-pointer with 6:43 remaining in the game. The Hawks quickly scored six straight, with Johnson's jumper restoring a double-digit lead, and weren't threatened again.
Jamal Crawford scored 20 points for the Knicks, who were trying for their first four-game winning streak of the season. New York still hasn't won more than three in a row since a six-game winning streak from Jan. 2-13, 2006.
The Knicks fell to 23-57 and still need one more victory to avoid tying the franchise record of 59 losses, which they matched just two years ago during Larry Brown's only season.
Wilson Chandler added 18 points and Zach Randolph had 17.
The Hawks made 14 of 21 shots in the first quarter, building a 34-23 lead behind 16 points from Johnson. The lead ballooned to 21 on Horford's three-point play with 5:01 left in the first half, and Atlanta led 62-43 at the break.
