The Reds last triumphed on the banks of the River Trent on September 28, when they beat east midlands rivals Derby.
And Mick McCarthy's side ensured it was five matches without a home success for Forest to make it 10 points from four games for the Championship's form side.
The Reds, in contrast, are on a run of just two wins in nine games, and found themselves dropping out of the play-off places.
It was a mystery how the first half ended without goals, with both sides having carved out solid openings.
David McGoldrick had a powerful strike deflected the wrong side of the post for Ipswich while, from the resulting corner Daryl Murphy planted a header narrowly wide.
Ipswich had started the stronger, with Frank Nouble only denied a fine solo goal by a strong save from Karl Darlow after the forward had carried the ball half the length of the pitch.
Forest improved, however, with Andy Reid twice coming close, before the game's controversial moment, which saw Simon Cox prod the ball around Dean Gerken before going down as the keeper slid in at his feet in the 19th minute.
Replays did suggest that Cox had started to fall before the keeper made contact.
But it was still a big call from referee Scott Mathieson, particularly given that Cox had already been booked for attempting to bring down Nouble when he broke quickly - and could have been sent off had he been shown a second yellow for simulation.
Cox was unlucky when he steered a header against the bar, while Jamie Mackie was thwarted as Gerken pushed away his rising shot.
Greg Halford might have done better when Djamel Abdoun's corner curled towards him at the far post, but the defender completely failed to make contact.
McGoldrick, who, along with Luke Chambers and sub Paul Anderson, was returning to his former club, was denied for a second time when his driven shot was pounced on by Darlow, just before the interval.
Forest should have taken the lead just before the hour mark, when Reid delivered an outstanding ball from the left, right across the face of goal.
Cox was arriving at the far post, where he only had to convert, but Gerken was quick off his line to make an outstanding save at his feet.
And they spurned another opportunity when substitute Darius Henderson attacked a Henri Lansbury free-kick - but sent his header straight into the arms of a well-placed Gerken.
The unlikely figure of Christophe Berra almost netted a well-worked winner for Ipswich, as he charged right through the centre, into the box, before striking a low shot that required Darlow to push away, diving to his left.