Celtic's championship celebrations were dampened considerably by this shock defeat. The SPL trophy was presented at the end of the match, but Dunfermline taking all three points was certainly not part of the script.
After Barry Nicholson had put the Pars ahead in the first half it looked like normal service had resumed when Henrik Larsson equalised shortly after the break, but incredibly Dunfermline regained the lead through Gary Dempsey which they held to the end with some stout defending.
Celtic nearly made an early breakthrough when Aiden McGeady's cross was met powerfully by Alan Thompson, but his header was well saved by Derek Stillie at the expense of a corner.
After good interplay between Neil Lennon and Larsson, Chris Sutton shot high over before Larsson's cut back fell just behind Sutton.
Dunfermline threatened briefly when Stanislav Varga's poor clearance allowed Dempsey a sight of goal, but his shot was easily gathered by David Marshall.
Thompson's quickly taken corner found Lennon alone on the 18-yard line but his powerful drive was inches high.
After some superb skill, McGeady sent in an inviting cross but Larsson for once was slow to react.
The visitors took the lead after Marshall did well to parry Derek Young's shot, but when Lee Bullen crossed to the back post Nicholson was on his own to volley home.
Despite intense Celtic pressure, Dunfermline nearly increased their lead shortly before half-time but Bullen's header was just too high.
Larsson equalised at the start of the second half when the Swede glanced home Thompson's corner at the near post.
If Celtic thought they were back in control they were rudely awakened when Dempsey stepped forward and shot low into the corner of the net from 30 yards, with Marshall at fault.
Celtic were stunned by this setback and laid siege to the Dunfermline goal. Sutton's header came back off the post before Johan Mjallby's volley from the rebound was brilliantly touched over by Stillie.
Noel Hunt nearly made it three for Dunfermline when he nipped between Varga and Mjallby, but Marshall managed to block his shot.
McGeady shot narrowly over and then Stillie produced a miraculous save to deny Craig Beattie.
Varga somehow managed to miss from only two yards after Beattie's cross reached them and then Shields blocked another Varga effort to deny Celtic an equaliser.