The two were locked in a sudden-death playoff, but Mother Nature eventually had her hand in deciding the outcome. With the sun gone while the pair were playing two extra holes, tournament officials and the players agreed to call it quits and declared both Montgomerie and Langer co-champions.
'It seems somewhat fitting to share this first place,' said Langer, who went 2-0-1 with Montgomerie as a partner in this year's Ryder Cup. 'We both played great. We both deserved to win, but Mother Nature wouldn't allow us to continue.'
Monty and Langer on sharing win.
Montgomerie was able to extend his streak of consecutive years with at least one win on the European Tour to 10, though he strung it out as long as possible. It took him until the final event of the season, beyond 72 holes of regulation, two sudden-death playoff holes and then, ultimately, darkness.
'I'd like to say that it's very fitting that this tournament should be tied, and especially the two people that have tied it,' said Montgomerie. 'I have a great respect for this man. I think it's only right that time didn't allow us to finish.'
Langer shot a final-round 4-under 67 to get to 3-under-par for the tournament, and Montgomerie posted a 1-under 70 to match the 281 total.
Montgomerie came to the 18th needing only a par to win it outright, but missed the eight-foot putt. Birdies on both 16 and 17 got him into that position.
Langer, who hadn't broken par until Sunday, had one of the day's best rounds. Three birdies, an eagle and a lone bogey brought him from three down to tie Montgomerie in regulation.
It was just the second time in European Tour history that dual winners have been crowned. Coincidentally, the first time also involved Langer.
Renton Laidlaw wraps up the event.
The 1986 Lancome Trophy was shared by the German and Seve Ballesteros at Saint Nom-la-Breteche after six playoff holes.
Overnight leader Bradley Dredge posted a 2-over-par 73 that dropped him from first and into sole possession of third place. He, along with Langer and Montgomerie, were the only three to be under par for the week.
First- and second-round leader Angel Cabrera continued to implode with a 3-over 74 Sunday, but he did finish in a tie for fourth with Australian Peter O'Malley, who fired a 2-under 69.
Cabrera opened with a wonderful 8-under 63 on Thursday, and led by as much as eight strokes at one point, but watched his firm grasp on the tournament slip away over the weekend.
World No. 5 Sergio Garcia shot a 2-over 73 to finish in a tie for seventh with Adam Scott at plus-3, a stroke back of sixth place Jarmo Sandelin.
Retief Goosen claimed his second straight Order of Merit title, beating out Padraig Harrington as both struggled all week with their games. Goosen finished at plus-12, with Harrington at plus-13.
'It's been pretty disappointing for the two of us the way we've been playing the last couple of weeks,' said Goosen.
'But you've got to play pretty well for a year or so to defend this title, so it's great to come through and pull it off.'
The 33-year-old South African became the first player since Sandy Lyle in 1980 to clinch the money title with just one victory during the season. Goosen captured the Johnnie Walker Classic in Australia in late January.
He follows in the footsteps of Englishmen Charlie Ward (1949) and Peter Oosterhuis (1972, 1973 and 1974), Ireland's Christy O'Connor (1962), Spaniard Ballesteros (1977, 1987) and Scotsmen Lyle (1980) and Colin Montgomerie (from 1994 to 1999) in successfully defending the European Tour's Order of Merit crown.
Full-field scores from the Volvo Masters