Tariqe Fosu scored Brentford’s first home goal for 321 minutes, but it was not enough to earn the win they needed to keep alive realistic hopes of automatic promotion.
Fosu’s speculative long-range shot was fumbled over the line by former QPR goalkeeper Alex Smithies to equalise after Kieffer Moore’s penalty.
The Bees had three good chances to take the lead in the first half, and piled on the pressure in the last 20 minutes, but Smithies stood firm to keep them out.
While Brentford can still mathematically reach second place, this result – their sixth draw in seven games – coupled with Watford’s win at Norwich, leaves them 10 points behind the Hornets with only four games to play.
It was another frustrating game for Brentford, who at least looked better in the last 20 minutes than in recent home matches.
They could have been ahead at the break if Marcus Forss had scored from inside the six-yard box when Ivan Toney headed back Fosu’s deep left-wing cross, and if Smithies had not denied both Bees strikers.
But it was Cardiff who went ahead after the break when Ethan Pinnock handled Curtis Nelson’s header at a free-kick, and Moore sent David Raya the wrong way from the spot.
Fosu quickly equalised from fully 30 yards with his fourth goal of the season and the last 20 minutes was all Brentford.
A long-range Sergi Canos shot bounced off Smithies’ chest, before the keeper saved a Toney volley at the second attempt.
The Bees were camped in the Cardiff area and Thomas Frank even threw on centre-half Charlie Goode as a third striker for the last few minutes.
But it was not enough and while Brentford have sorted out their problems at the back and are unbeaten in eight games, they have now drawn 15 matches this season – the second highest total in the Championship – and that is why they will have to settle for the play-offs.
Brentford: Raya, Jansson, Norgaard, Pinnock, Roerslev (Canos 58), Janelt (Ghoddos 58), Jensen, Mbeumo (Marcondes 67), Fosu (Goode 90), Forss, Toney.