The result denied Billy Davies' side what would have been a club record 13th consecutive home win.
But, more significantly, it also ensured that Newcastle could no longer be denied a top-two finish and promotion back into the top-flight.
Both sides - who could meet again in the play-offs in a few weeks time - spurned great opportunities to snatch all three points.
But it will have been Forest who were most disappointed after dominating for long periods.
Forest could have taken the advantage within four minutes when a free-kick delivery from Radoslaw Majewski picked out Dexter Blackstock, but the striker's six-yard header was aimed right at keeper David Marshall.
Cardiff were a real threat from set-pieces, however, with a Joe Ledley shot deflected over the bar by an outstanding challenge from Luke Chambers and Darcy Blake connecting so powerfully with a downwards header that the ball bounced up over the bar.
A missed header from Anthony Gerrard almost proved costly as Robert Earnshaw skipped through the Cardiff defence, only to be denied by a fine save from Marshall, who stretched out a leg to push away the striker's shot.
There were more missed opportunities for Forest as Nathan Tyson failed to connect with a clever, incisive ball from Guy Moussi at the far post.
But the worst miss was committed by Chris Cohen who, after Tyson had lashed a superb ball across the face of goal, completely failed to make contact with an air shot at the far post.
Ross McCormack almost shocked Forest with a clever free-kick as he unexpectedly powered a shot towards the near post from wide out on the left, with Lee Camp saving bravely as Michael Chopra challenged.
It was Forest who continued to push in the run-up to half-time, with Earnshaw seeing an angled shot charged down and Chambers forcing another stop from Marshall with a looping header.
Dexter Blackstock threatened again after the break, firing another header straight at the keeper, this time from a Cohen cross.
McCormack endured a mad 30 seconds as he forced a fine stop from Camp with a superb long-range drive, but then got booked for hacking down Gunter when the Forest man carried the ball out of the box.
Earnshaw flicked an instinctive header narrowly wide of the post and Blackstock, following another moment of defending from Gerrard, was denied by another vital save from Marshall, who pushed away the striker's angled shot.