The stalemate at the City Ground left Billy Davies' men 11 points behind second-placed West Brom with four games remaining and guaranteed leaders Newcastle an immediate return to the Premier League ahead of their game against Sheffield United later this evening.
Forest remain near certainties to claim a play-off berth, while Cardiff are now six points clear of seventh-placed Blackpool.
Both sides had chances in a largely even opening period, with home goalkeeper Lee Camp making a stunning early save to deny Darcy Blake and Robert Earnshaw wasting a gilt-edged chance for the Reds soon after.
Forest picked up the pace after the interval, but neither side was able to find a breakthrough, ensuring the Bluebirds were involved in their first 0-0 of the season.
The result also brought Forest's record-equalling run of home league wins to an end as they failed to record a 13th consecutive home victory.
Earnshaw returned to face his former club as one of four changes to the Forest side that drew 1-1 at Bristol City on Saturday.
Cardiff were without top scorer Peter Whittingham, who picked up a knock in the dramatic 2-1 win over rivals Swansea.
However, Joe Ledley made his first start since January following his recovery from surgery on both hips.
The visitors started brightly and twice went close inside the opening six minutes.
Ledley saw a goalbound shot superbly blocked by Luke Chambers and from the resulting corner Camp showed sensational reflexes to tip Blake's header over the crossbar.
Blake was involved at the other end moments later when he misjudged a bouncing ball to present Earnshaw with a clear run on goal, but David Marshall made a fine stop with his feet to deny the striker.
The Bluebirds were soon back on the front foot, with a succession of Ross McCormack corners causing panic in the home defence.
Forest responded with Guy Moussi's cross narrowly evading Nathan Tyson at the far post.
Another McCormack set-piece forced Camp into action in the 20th minute, the Reds goalkeeper reacting well to palm away an inswinging free-kick.
The hosts came agonisingly close to breaking the deadlock seven minutes later as Chris Cohen somehow failed to make contact with Tyson's right-wing cross with the goal at his mercy.
The only other action of note before the break came in the 35th minute as Michael Chopra latched on to a weak header from Forest defender Kelvin Wilson and shot narrowly wide, only to be flagged offside by the linesman, sparking confusion in the visiting ranks.
Forest started the second period with renewed vigour but did not trouble Marshall until the hour mark, when Dexter Blackstock planted a header into the arms of the Cardiff keeper.
Camp was then forced to palm away a long-range effort from McCormack, who sparked a melee seconds later with a cynical body check on former Cardiff full-back Chris Gunter.
After referee Chris Foy had calmed things down, Earnshaw went close again for Forest with a header from Tyson's cross.
The hosts had another opportunity with 12 minutes remaining, but Marshall dived low to his right to deny Blackstock after the striker had burst clear.
Cardiff held on thereafter, although Marshall and team-mate Anthony Gerrard almost came to blows following a furious exchange in the visitors' penalty area.