Johnson's game-winning shot capped an improbable rally from a 16-point second-half deficit for the Nets (11-21), led by a season-high 29 points from point guard Deron Williams.
Brooklyn trailed, 77-61, late in the third quarter, but Williams scored 18 in the second half and helped set the stage for Johnson's last-second shot.
Kevin Durant led the Thunder (25-7) with 24 points. Oklahoma City was playing its fourth straight game without injured All-Star guard
The loss was the second straight for the Thunder, only the second time they've lost two in a row this season.
New York 105, at San Antonio 101:
Golden State 123, at Miami 114:
at Cleveland 87, Orlando 81 (OT):
at Chicago 94, Boston 82:
at Portland 134, Charlotte 104:
Memphis 99, at Phoenix 91:
Philadelphia 113, at Sacramento 104: