With the minutes ticking away and the scores level at 1-1, John Obi Mikel shot on goal, Claudio Pizarro flicked the ball on and Kalou raced in to tuck it in under Newcastle keeper Shay Given's body.
The Newcastle players went mad as Pizarro appeared to hit the ball from an offside position, but referee Mike Riley awarded the goal.
Goals from Michael Essien and Nicky Butt enlivened an otherwise inept performance from both sides.
Third-choice goalkeeper Henrique Hilario was called into action on four minutes after a slip-up by Alex let in Obafemi Martins, but the Nigerian striker was just too slow to take advantage and he collected the ball coolly.
Chelsea's first decent attack on ten minutes saw Shaun Wright-Phillips zip a byline cross to Michael Ballack, but the Chelsea captain flashed a right-footed drive high over Given's goal.
The Magpies should have scored on 14 minutes when Mikel was dispossessed in midfield by Butt, who sent Martins clear on goal but the striker was not quick enough to get away from the challenge from Alex.
Lone striker Kalou delivered a spiky right-footed shot on target from eight yards, but Given was quick to parry the ball away for a corner.
He produced an even better save on 21 minutes when he scooped away a fierce Mikel drive which took a deflection on its path towards goal.
It was certainly Given's half as he was in the correct spot to smother an unmarked Alex header on 26 minutes.
But he was not at fault as Chelsea took the lead seconds later as Wright-Phillips' shot was deflected off Steven Taylor and Essien tucked home a smart left footer from six yards.
Butt almost produced the best own-goal ever when on 46 minutes when the former England midfielder lashed towards his own goal from outside his area, but once again Given acrobatically tipped the ball over his bar.
But within five minutes of the restart, the visitors were level as Charles N'Zogbia skipped past Mikel on the left and sent in a low drive across goal.
Martins touched the ball on and then Wayne Bridge and Butt scrambled for the ball on the line with Butt claiming the final touch
Chelsea sped up field and Ballack was unlucky with a shot from the edge of the box, but once again Given smothered the ball.
Avram Grant substituted Joe Cole with Pizarro on 65 minutes to a crescendo of boos from the Chelsea fans.
Injury-plagued Magpies striker Michael Owen returned to the fray on 74 minutes at the expense of Martins
The game limped on until the final four minutes when Chelsea's luck held and three points were gained at the expense of the unfortunate visitors.