Johnson scored 29 of his points in the third, tying Milwaukee's Michael Redd (2002) for the most 3-pointers ever in a single quarter. He finished the game 10-of-14 from beyond the arc.
Andray Blatche put in 20 points and Paul Pierce added 14 off the bench for the Nets, who put the game away with a 17-3 burst starting the big quarter.
Deron Williams supplied 13 points and 13 assists.
The 76ers stumbled to a seventh straight loss despite 17 points off the bench from James Anderson.
Thaddeus Young added 14 for Philadelphia.