The German registered his first win as Cottagers boss as the visitors toiled, with manager Alan Pardew serving the first match of his seven-game stadium ban
Magpies boss Alan Pardew missed the clash as he began serving his sanction for a headbutt on Hull City's David Meyler, having been given a three-game stadium suspension and four-game touchline ban by the FA.
Assistant manager John Carver took charge in Pardew's stead but he could not inspire the visitors to a third consecutive win.
And Pardew, reportedly watching the action from a hotel suite in London, will have been largely unimpressed with his side's display as bottom-club Fulham produced a dominant second-half performance to take the points.
|BATTLE AT THE BOTTOM
16. West Brom
17. Crystal Palace
Newcastle were boosted by the return of captain Fabricio Coloccini, while Papiss Cisse came in for the injured Loic Remy.
The early stages were scrappy with few goalscoring opportunities, although Fulham did enjoy the better start without really troubling the Newcastle defence.
But it was the visitors who eventually had the first real sight of goal, as Paul Dummett curled over from a free kick midway through the first half.
Krul was the first of the two goalkeepers to be called into action just after the half-hour mark, the Dutchman diving to his right to keep out Lewis Holtby's effort from the edge of the area.
The visitors gradually grew into the game and would have taken the lead before the break had David Stockdale not produced a fine reaction save to prevent Cisse from turning home Moussa Sissoko's right-wing cross.
Fulham did have the ball in the net almost immediately after the break but Pajtim Kasami's strike was ruled out, after John Heitinga was ruled to have strayed offside before heading the ball back for the Swiss winger.
Newcastle then crafted a good opportunity at the other end but Luuk de Jong could only shoot tamely wide after latching on to Yoan Gouffran's pass.
Magath's men quickly began to dictate play and Pardew will have been thankful as the offside flag denied Fulham's teenage striker Cauley Woodrow.
Woodrow looked to have netted his first goal for the club when he prodded home a rebound after Heitinga's rasping drive had crashed off the underside of the crossbar and out, only for the linesman to rule out the effort.
But Fulham were finally rewarded for their initiative after 68 minutes when a Krul error handed them the lead, just after Stockdale had denied Cisse for a second time.
Substitute Dejagah cut in from the left and fired in a low, right-footed effort, which Krul allowed to bounce under his grasp and into the bottom corner.
Newcastle, however, pressed in the final stages to try and find a leveller and were denied a penalty right at the death.
Referee Howard Webb refused to point to the spot when Heitinga appeared to handle from Krul’s effort after the goalkeeper had come up for a late corner, ensuring that Fulham held on - although the London club remain four points adrift of safety.