The Saints striker equalized five minutes from time after a Berbatov opener as the relegation strugglers shared the points.
The Saints striker kept his cool to slam high into the net five minutes from time after referee Phil Dowd had pointed to the spot for a handball from Fulham defender Chris Baird.
Fulham thought it was set for all three points after Dimitar Berbatov’s eighth minute strike, but Martin Jol’s side has now recorded just one victory in its last 11 matches and is increasingly being dragged towards the bottom three.
Southampton remains 17th in the table and now faces a season-defining run of games, with four of the next five fixtures against sides in the current top six.
Jol made three changes to the Fulham side that lost 4-0 at Liverpool, bringing Philippe Senderos, Steve Sidwell and Hugo Rodallega into the starting lineup. Southampton made just one change to the side that was beaten by Sunderland as Steven David replaced Emmanuel Mayuka.
Jol would have hammered into his players the importance of the festive period as Fulham looks to escape from a potential relegation fight, and the home side started brightly.
The Cottagers could have taken the lead just three minutes in when, after good work from Rodallega, Sidwell picked up the ball and fired a powerful effort just wide from the edge of the penalty area.
In the eighth minute, Fulham did score the goal that calmed nerves around Craven Cottage. Sascha Riether whipped in a low cross from the right that the Southampton goalkeeper could only palm into the path of Berbatov. The Bulgarian made no mistake in turning the ball into a virtually empty net for his first goal in seven appearances.
He removed his shirt to unveil a message - ‘keep calm and pass me the ball’ - and referee Phil Dowd calmly booked him for the celebration.
Southampton settled down and showed fighting spirit without particularly threatening in the final third. Jack Cork forced a save from Mark Schwarzer with a shot from 25 yards before the break before Nigel Adkins’ started to control large portions of the game after the break.
Jason Puncheon skimmed an attempt wide of the post two minutes after the restart but the Saints struggled to break down Fulham’s stubborn defense.
Twelve minutes from time, the Saints came close to an equalizer but Lambert volleyed a yard over the bar from Luke Shaw’s cross.
Then, Baird stupidly handled as he attempted to clear a corner. Lambert stepped up to slam his spot kick into the top corner.
All of a sudden, the game opened up. Gaston Ramirez forced Schwarzer into action with a dipping strike from 20 yards before Sidwell whipped a curling shot just off target.