Paul McGowan's late penalty gave St Mirren a point against Celtic, who had Victor Wanyama sent off in a match overshadowed by refereeing errors.
Kris Commons met Efe Ambrose's cross to net early for the visitors in Paisley.
Saints had Marc McAusland's header cleared off the line by Beram Kayal before referee Bobby Madden issued red to Wanyama for a foul on McGowan.
And McGowan levelled from the spot late on after Emilio Izaguirre was judged to have tripped Esmael Goncalves.
At least three of referee Madden's key decisions in this match were strongly disputed, with Celtic boss Neil Lennon stating afterwards it was "by far the most appalling refereeing performance" he'd seen this season "by a long, long way".
Madden missed Georgios Samaras's handball in the box; dismissed Wanyama for what seemed a soft flick at McGowan; and awarded a spot-kick to St Mirren when no touch on Goncalves was evident.
Coming away with just a point here means Celtic can still clinch the Scottish Premier League title next weekend if they beat Hibs and Motherwell lose against St Mirren.
Meanwhile, the Buddies, who move into 10th, will be glad to have got their first point and goal against Celtic in nine league meetings.
Neil Lennon's men brought mutual good feeling to St Mirren Park pre-kick-off, forming a guard of honour for their opponents to walk through in recognition of the Paisley side's League Cup triumph.
But the Hoops quickly shelved the sentimental stuff when an early Gary Hooper shot was followed by their opening goal.
Kayal's cross was only headed half-clear and Ambrose chipped the ball back for Commons to nod his 14th goal of the season into the bottom corner of Craig Samson's net.
Saints responded well, with Paul Dummett's side-foot effort touched wide by the on-rushing Celtic goalkeeper Fraser Forster before cup final goal-scorer Conor Newton drove a 20-yarder narrowly over.
Commons made a mess of another chance from Joe Ledley's delivery, which Celtic were nearly made to pay for when McAusland's header was cleared off the line by Kayal at the other end.
Then silky wing-play by Gary Teale ended with a tasty cross for Thompson to head wide for the Buddies.
St Mirren did have the ball in the net on the half-hour when Teale's cross from the left sailed directly in, but referee Madden decided Dummett had fouled Forster in the process.
Visiting fans sensed a second goal when Commons released Hooper however his screwed right-foot shot was not on their script.
Celtic lost Commons to an ankle injury before one final first half flashpoint when St Mirren claimed the arm of Samaras had connected with Teale's corner, but no penalty was awarded.
More controversy followed after the break, referee Madden showing Celtic's Wanyama a straight red card, perhaps harshly, for a late foul on McGowan.
Naturally, Saints pushed and both Teale and David van Zanten saw left-foot strikes flash over the bar.
And with 10 minutes remaining, the home side got the equaliser from the penalty spot.
Referee Madden judged that Goncalves had been tripped on the edge of the box by Celtic's Izaguirre, but doubt existed about whether there was any touch at all.
Nevertheless, McGowan stepped up to side-foot down the middle to bring his side level.
St Mirren were almost gifted the win when Forster fumbled an injury-time cross which nearly fell to substitute Sander Puri.
- 01 Samson
- 02 van Zanten
- 03 Dummett
- 06 Goodwin
- 14 McAusland
- 10 McGowan
- 21 Teale
- 24 Newton
- 29 J McGinn (Carey - 66' )
- 09 Thompson Booked
- 77 Goncalves (Puri - 88' )
- 16 Adam
- 05 Mair
- 11 Carey
- 17 Mclean
- 88 Puri
- 19 Parkin
- 27 Guy
- 01 Forster
- 03 Izaguirre
- 04 Ambrose
- 06 Wilson
- 67 Wanyama Dismissed
- 15 Commons (Stokes - 46' )
- 16 Ledley
- 21 Mulgrew Booked
- 33 Kayal
- 09 Samaras Booked (Watt - 90' )
- 88 Hooper (McGeouch - 72' )
- 24 Zaluska
- 05 Gershon
- 18 Rogic
- 20 McCourt
- 46 McGeouch
- 10 Stokes
- 32 Watt
Live Text Commentary
Full Time The referee blows his whistle to end the game.90:00 +0:46 Substitution
Substitution Tony Watt replaces Georgios Samaras.89:17
Kelvin Wilson gives away a free kick for an unfair challenge on Steven Thompson. Direct free kick taken by Craig Samson.88:00 Substitution
Substitution Esmael Goncalves leaves the field to be replaced by Sander Puri.86:56
Gary Teale takes a shot.85:53
The referee gives a free kick against Paul McGowan for handball. The free kick is delivered right-footed by Gary Teale from right wing, Georgios Samaras manages to make a clearance.83:17
Steven Thompson takes a shot. Fraser Forster makes a save.80:38
The assist for the goal came from Esmael Goncalves.80:38 Goal scored
Goal! - Paul McGowan - St Mirren 1 - 1 Celtic Power penalty scored by Paul McGowan. St Mirren 1-1 Celtic.79:46
Unfair challenge on Esmael Goncalves by Emilio Izaguirre results in a Penalty.77:41
Paul McGowan challenges Georgios Samaras unfairly and gives away a free kick. Free kick taken by Charlie Mulgrew.76:23
Outswinging corner taken right-footed by Gary Teale from the right by-line, Steven Thompson produces a header from inside the area that goes over the crossbar.71:26 Substitution
Substitution Dylan McGeouch joins the action as a substitute, replacing Gary Hooper.69:57
David van Zanten produces a right-footed shot from deep inside the penalty box which goes wide of the left-hand post.68:48
Corner taken by Graham Carey from the right by-line, clearance made by Anthony Stokes.66:34
Graham Carey takes the direct free kick.66:34 Booking
Booking Georgios Samaras is cautioned.66:17
Free kick awarded for a foul by Georgios Samaras on Gary Teale.65:30 Substitution
Substitution Graham Carey on for John McGinn.65:13
Gary Teale produces a left-footed shot from just outside the box that goes wide left of the goal.
The assistant referee flags for offside against Georgios Samaras. Free kick taken by Craig Samson.54:49
Free kick taken by Jim Goodwin.54:49 Dismissal
Dismissal Victor Wanyama is shown a red card for serious foul play.54:37
Victor Wanyama challenges Paul McGowan unfairly and gives away a free kick.53:28
Free kick awarded for an unfair challenge on Paul Dummett by Emilio Izaguirre. Craig Samson restarts play with the free kick.51:18
Free kick awarded for a foul by Victor Wanyama on John McGinn. Jim Goodwin takes the direct free kick.45:01
The referee gets the second half underway.45:01 Booking
Booking Steven Thompson booked for dissent.45:01 Substitution
Substitution Anthony Stokes on for Kris Commons.45:00 +11:59 Half time
Half Time The players leave the pitch at half time.45:00 +3:30
Corner from right by-line taken by Gary Teale.45:00 +2:39
Corner from right by-line taken by Gary Teale.36:36
Gary Hooper takes a shot.32:08
Joe Ledley challenges David van Zanten unfairly and gives away a free kick. David van Zanten restarts play with the free kick.28:25
Outswinging corner taken left-footed by Charlie Mulgrew from the right by-line, Steven Thompson makes a clearance.25:54
Inswinging corner taken right-footed by Gary Teale from the left by-line, Paul Dummett concedes a free kick for a foul on Fraser Forster. Fraser Forster restarts play with the free kick.24:12
Shot by John McGinn from outside the box goes over the net.23:28
Corner taken by Gary Teale from the left by-line, clearance by Victor Wanyama.22:56
Unfair challenge on Gary Teale by Emilio Izaguirre results in a free kick. Direct free kick taken by David van Zanten.18:45
Kelvin Wilson challenges Steven Thompson unfairly and gives away a free kick. Gary Teale takes the free kick.18:12
Outswinging corner taken left-footed by Charlie Mulgrew.17:20
Emilio Izaguirre fouled by Conor Newton, the ref awards a free kick. Emilio Izaguirre takes the direct free kick.16:39
Unfair challenge on John McGinn by Efe Ambrose results in a free kick. Jim Goodwin takes the direct free kick.15:29
Headed effort from deep inside the penalty area by Steven Thompson misses to the right of the target.14:46
Kris Commons has an effort at goal from the edge of the area that misses to the right of the target.13:00
Floated corner taken right-footed by Gary Teale, clearance made by Victor Wanyama.12:16
Corner taken right-footed by Gary Teale, Marc McAusland takes a shot. Efe Ambrose gets a block in.9:55
Conor Newton produces a right-footed shot from inside the area that clears the bar.8:23
Short corner taken by Gary Teale from the right by-line, clearance made by Gary Hooper.7:59
Paul Dummett takes a shot. Save by Fraser Forster.5:34
Assist by Efe Ambrose.5:34 Goal scored
Goal! - Kris Commons - St Mirren 0 - 1 Celtic Kris Commons scores a headed goal from inside the penalty box. St Mirren 0-1 Celtic.5:16
Kris Commons takes the outswinging corner, clearance made by Jim Goodwin.4:15
Unfair challenge on Kris Commons by Jim Goodwin results in a free kick. Shot on goal comes in from Charlie Mulgrew from the free kick.2:47
Gary Hooper has an effort at goal from deep inside the area missing to the left of the target.1:20
Inswinging corner taken left-footed by Charlie Mulgrew from the left by-line to the near post.0:00
The referee gets the match started.
Live data and text provided by our data suppliers