Cardiff earned their first away league win over Reading since November 2011 when they won 2-1 under Malky Mackay.
Reading's hopes of a Championship play-off spot remain intact after Yakou Meite's late equaliser against Cardiff.
Meite headed in Sam Baldock's fine cross from close range in the fourth minute of stoppage time to make it 1-1.
It had seemed Cardiff would take all three points after Kieffer Moore's penalty with five minutes remaining.
The draw leaves Reading seventh, four points behind Barnsley who have a game in hand over the Royals, while Cardiff are eighth but out of contention.
Cardiff's hopes of a top-six finish have all but ended - a fact acknowledged by Bluebirds boss Mick McCarthy - with the Royals knowing anything less than a win would see them lose valuable ground in the fight for a play-off spot.
Reading boss Veljko Paunovic made two changes from the side beaten 2-0 by Watford, with Omar Richards and top scorer Lucas Joao returning, while Cardiff made one change from the side held at home by Blackburn with Joe Ralls replacing Josh Murphy.
The visitors were certainly playing for lower stakes than Reading and with the pressure off they started brightly with Harry Wilson's run culminating in a shot that Rafael did really well to turn away.
The stakes seemed to be weighing on the hosts and it was 29 minutes before they produced a shot on target, but Meite's attempt at flicking the ball home audaciously was easily stopped by Cardiff goalkeeper Alex Smithies.
Ovie Ejaria's shot from 20 yards on 51 minutes was the next time Smithies was tested in a contest full of niggle and tetchy fouls and short on quality and clear-cut opportunities.
Joao almost caught out Cardiff as he received a clever free-kick and fired at goal on the turn, but Smithies saved his effort at the near post in a costly incident as Joao injured his shoulder as he fell, with the striker unable to continue.
Reading's urgency increased in the second half and they began to look more of a threat thanks to increased possession higher up the pitch, with Meite wasting a great chance on 69 minutes when he shot over after being found unmarked in the penalty area.
Cardiff did not come close in the second half until they had two chances within a minute as Moore shot tamely at Rafael, before they almost pinched the lead when Harry Wilson broke clear and dinked the ball over the goalkeeper, but Andy Yiadom cleared the ball off the line.
The Bluebirds continued to soak up the pressure before a mistake seemed to have won them the contest as Richards switched off and fouled Moore, who fired the penalty into the roof of the net with five minutes remaining.
However, Reading were not to be denied and Meite headed home from sub Baldock's fine cross with Aden Flint unable to deflect the ball wide.
- Line-upsMatch StatsLive Text
Line-upsReading
Formation 4-2-3-1
33Cabral Barbosa17Yiadom29Holmes6Moore3Richards8Rinomhota28Laurent11Meite7Olise14Ejaria18Lucas João
- 33Cabral Barbosa17YiadomSubstituted forBaldockat 90'minutes29Holmes6Moore3RichardsSubstituted forAlukoat 90'minutes8RinomhotaSubstituted forSwiftat 77'minutes28Laurent11Meite7OliseSubstituted forTetekat 90'minutes14Ejaria18Lucas JoãoSubstituted forPuscasat 58'minutes
Substitutes
- 2Pontes Esteves9Baldock10Swift15Gibson22Southwood24Aluko30Semedo34Tetek47Puscas
Cardiff
Formation 3-4-2-1
12Smithies16Nelson5Flint30Brown28Sang21Pack6Vaulks38Ng23Wilson8Ralls10Moore
- 12Smithies16NelsonBooked at 46mins5Flint30BrownBooked at 78mins28Sang21PackBooked at 50minsSubstituted forMurphyat 70'minutes6Vaulks38Ng23WilsonSubstituted forOjoat 81'minutes8Ralls10Moore
Substitutes
- 1Phillips2Osei-Tutu11Murphy15Williams19Watters27Ojo29M Harris33Hoilett40Colwill
Referee:John BrooksMatch StatsHome TeamReadingAway TeamCardiffPossessionHome66%Away34%ShotsHome15Away10Shots on TargetHome4Away5CornersHome3Away3FoulsHome17Away16Live TextPost update
Match ends, Reading 1, Cardiff City 1.
90'+6'Full Time
Second Half ends, Reading 1, Cardiff City 1.
90'+4'goalGoal!
Goal! Reading 1, Cardiff City 1. Yakou Meite (Reading) header from the centre of the box to the high centre of the goal. Assisted by Sam Baldock with a cross.
90'+4'Post update
Attempt blocked. John Swift (Reading) left footed shot from outside the box is blocked. Assisted by Dejan Tetek.
90'Substitution
Substitution, Reading. Dejan Tetek replaces Michael Olise.
90'Substitution
Substitution, Reading. Sam Baldock replaces Andy Yiadom.
90'Substitution
Substitution, Reading. Sone Aluko replaces Omar Richards.
88'Post update
Attempt missed. Aden Flint (Cardiff City) header from the centre of the box is just a bit too high. Assisted by Will Vaulks with a cross following a corner.
88'Post update
Corner, Cardiff City. Conceded by Thomas Holmes.
87'Post update
Goal! Reading 0, Cardiff City 1. Kieffer Moore (Cardiff City) converts the penalty with a right footed shot to the top left corner.
85'Post update
Penalty conceded by Omar Richards (Reading) after a foul in the penalty area.
85'Post update
Penalty Cardiff City. Kieffer Moore draws a foul in the penalty area.
85'Post update
Attempt saved. Sheyi Ojo (Cardiff City) left footed shot from outside the box is saved in the bottom right corner. Assisted by Will Vaulks.
83'Post update
Foul by Yakou Meite (Reading).
83'Post update
Alex Smithies (Cardiff City) wins a free kick in the defensive half.
81'Substitution
Substitution, Cardiff City. Sheyi Ojo replaces Harry Wilson.
81'Post update
Foul by Yakou Meite (Reading).
81'Post update
Ciaron Brown (Cardiff City) wins a free kick in the defensive half.
79'Post update
Foul by John Swift (Reading).
79'Post update
Curtis Nelson (Cardiff City) wins a free kick in the defensive half.
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Source: bbc.com