Petteway netted 16 of his total in the second half and Pitchford drained four 3-pointers for the Cornhuskers (14-10, 6-6 Big Ten), who snapped a 21-game road losing streak against ranked opponents.
It was the third consecutive win overall for Nebraska.
The Spartans (21-5, 10-3) dropped a fourth in seven games despite 18 points and four assists from Gary Harris.
The loss left Michigan State tied with Michigan atop the Big Ten Conference standings with three weeks remaining in the regular season.
Swim Week Miami Beach 2014 [PHOTOS]