A 2-1 win at the KC Stadium on Saturday afternoon means it is six wins on the spin for the Reds since Billy Davies returned to the club.
Promotion contenders Hull took the lead through George Boyd as he lined up against the side that nearly signed him in January but Darius Henderson and substitute Lewis McGugan netted the goals that earned three points and cemented a top-six place.
Match reaction - Billy Davies: "I thought we started not the brightest; we just didn't stick to our game plan and gave them too much space.
"They score a goal against the run of play, and second half we showed great courage and we went for it. We put on some very attacking substitutes and McGugan does what McGugan does best and gets the winner.
"We tried to win the game, especially at 1-1. We've given ourselves a great chance of the play-offs."
Match reaction - Steve Bruce: "We've done enough to win two matches, that's the biggest disappointment.
"I couldn't fault the way we played or the way we've gone about it.
"To be fair to Forest, they've gone for it and played three up front, but the attempts we've had off the line and the post - it's just one of those horrible ones where the luck goes against you.
"Unfortunately it wasn't our day."