Caroline Weir's strike was the first conceded by Chelsea in the Champions League this seasonChelsea will have to wait to confirm their place in the Women's Champions League quarter-finals after being held at Real Madrid.
Victory would have seen Emma Hayes' side qualify with two games to spare.
However, they fell behind to Caroline Weir's first-half strike after goalkeeper Ann-Katrin Berger's error.
Chelsea equalised in the second half when Guro Reiten's penalty hit the post, rebounded off Madrid keeper Misa and went in.
The Blues will reach the last eight if they win against Albanian side Vllaznia on December 16.
Chelsea have 10 points from four games in Group A, five ahead of third-placed Madrid with a much better goal difference.
They will also fancy their chances of winning in Albania, against a Vllaznia side who have yet to earn a point or score a goal, have conceded 19 times and were beaten 4-0 by Paris St-Germain earlier on Thursday.
Unusual Berger mistake costs Chelsea
Chelsea entered this game with a perfect group stage record, including a 2-0 victory over Madrid at Kingsmeadow two weeks ago. Another win here would have seen them surpass their disappointing 2021 campaign where they failed to get out of the group.
While much of the focus on Chelsea goes to their star-studded front line, goalkeeper Berger has been just as crucial to their strong European form, not conceding a goal in the 2022-23 Champions League before tonight.
The German may have been unsettled by treatment she needed to her foot just minutes before the Madrid opener, seemingly sustained as she went over awkwardly while diving for a long range Olga Carmona shot which flew just wide.
Whatever the reason, it was an uncharacteristic error by Berger as she attempted to pass the ball into midfield but instead only found ex-Manchester City midfielder Weir, who gratefully accepted the gift and slotted into the empty net from 22 yards.
This was the second time Weir has found the net against a Women's Super League side after leaving City in the summer, having scored the only goal to eliminate her old side from the Champions League in qualifying.
Chelsea were sloppy in midfield and while they dominated possession, 61% in the first 70 minutes, often gave the ball away in good positions.
They lost the ball just outside their own box with 10 minutes to go, leaving Carmona to break through - only for Berger to make a fine spreading save, a timely reminder of her importance and ability.
Blues get lucky with bizarre penalty
Chelsea manager Hayes described the win over Madrid two weeks ago as a "cagey affair" - there was no such caution here as the Blues hit the woodwork three times, with the final one falling in their favour.
They should have led inside two minutes when an Erin Cuthbert header from a corner was palmed away by Misa and fell to Sam Kerr who thumped the ball off the crossbar when she should have scored.
It was an off night for Kerr, who spurned a similarly clear opening half an hour later. The Australian was put through one-on-one against Misa by Lauren James, but pulled her shot onto the outside of the right post.
Instead it took an immense stroke of fortune for Chelsea to equalise, after Ivana Andres clumsily brought down Reiten in the area.
The Norwegian took the spot-kick which hit the keeper's right-hand post - only to deflect back off Misa's back and roll agonisingly over the line.
Kerr could have won it for Chelsea in the final minutes - and put her side into the quarter-finals - however she was denied one-on-one again by a superb save from Misa.
The 2021 finalists look likely to make amends this season for their group-stage elimination in 2021-22, but this must count as a wake-up call.
Line-ups
Real Madrid Femenino
Formation 4-2-3-1
1Rodríguez Rivero
5Andrés14Sousa Feitoza4Gálvez7Carmona
6Toletti21Zornoza
22del Castillo11Weir20Feller
10González
1Rodríguez Rivero5Andrés14Sousa Feitoza4Gálvez7Carmona6Toletti21ZornozaSubstituted forOrozat 74'minutes22del CastilloBooked at 21mins11Weir20FellerSubstituted forGarcíaat 90'minutes10GonzálezSubstituted forSvavaat 61'minutesSubstitutes
2Robles3Abelleira8Oroz9García13Gerard15Florentino16Hansen18Rodriguez23Svava24Olofsson27Camacho46FuenteChelsea Women
Formation 4-3-3
30Berger
7Carter26Buchanan4Bright16Eriksson
22Cuthbert5Ingle17Fleming
10James20Kerr11Reiten
30Berger7CarterBooked at 63mins26Buchanan4Bright16ErikssonSubstituted forCharlesat 45'minutes22Cuthbert5Ingle17FlemingSubstituted forKirbyat 45'minutes10JamesBooked at 66minsSubstituted forRytting Kanerydat 77'minutes20Kerr11ReitenSubstitutes
1Musovic3Nouwen9England13Svitková14Kirby15Périsset18Mjelde19Rytting Kaneryd21Charles27Abdullina28Cankovic32OrmanLive Text
Match ends, Real Madrid Femenino 1, Chelsea Women 1.
Second Half ends, Real Madrid Femenino 1, Chelsea Women 1.
Attempt missed. Sam Kerr (Chelsea Women) header from very close range is close, but misses to the left. Assisted by Erin Cuthbert with a cross following a corner.
Corner, Chelsea Women. Conceded by Rocío Gálvez.
Substitution, Real Madrid Femenino. Nahikari García replaces Naomie Feller.
Corner, Chelsea Women. Conceded by Misa.
Attempt saved. Sam Kerr (Chelsea Women) right footed shot from the centre of the box is saved in the top centre of the goal. Assisted by Guro Reiten.
Foul by Erin Cuthbert (Chelsea Women).
Maite Oroz (Real Madrid Femenino) wins a free kick in the defensive half.
Offside, Chelsea Women. Sam Kerr tries a through ball, but Guro Reiten is caught offside.
Sam Kerr (Chelsea Women) wins a free kick on the right wing.
Foul by Sofie Svava (Real Madrid Femenino).
Attempt missed. Caroline Weir (Real Madrid Femenino) left footed shot from outside the box is too high. Assisted by Maite Oroz.
Attempt saved. Olga Carmona (Real Madrid Femenino) left footed shot from the centre of the box is saved in the centre of the goal.
Attempt saved. Olga Carmona (Real Madrid Femenino) left footed shot from the left side of the box is saved in the top left corner. Assisted by Maite Oroz.
Offside, Chelsea Women. Guro Reiten tries a through ball, but Sam Kerr is caught offside.
Offside, Real Madrid Femenino. Sofie Svava tries a through ball, but Olga Carmona is caught offside.
Substitution, Chelsea Women. Johanna Rytting Kaneryd replaces Lauren James.
Erin Cuthbert (Chelsea Women) wins a free kick in the defensive half.
Foul by Maite Oroz (Real Madrid Femenino).
