Chris Coleman's side took control after half-time as the visitors were undermined by mistakes from Nicky Butt and debut-making American defender Oguchi Onyewu.Butt blundered with a dismal backpass in the 49th minute which let Helguson gallop through and thunder a shot beyond goalkeeper Steve Harper.
And the giant Onyewu, signed from Standard Liege on loan for the rest of the season, should have been sent off for a deliberate tug on Helguson when the striker was clean through in the 60th minute.
• Coleman salutes strikers
Four minutes later, though, McBride's sweeping right-footed shot - following brilliant work by substitute Papa Bouba Diop - confirmed Newcastle's first league defeat of 2007.
Obafemi Martins stoppage-time goal was just a consolation for the visitors.
Fulham were good value for a fine win after seeing their unbeaten run come to an end at Sheffield United on Tuesday.
Manager Coleman rang the changes in defence and was rewarded by sound displays from Philippe Cristanval and Carlos Bocanegra.
With new boy Onyewu a powerful, bruising presence alongside Titus Bramble at the heart of Newcastle's defence and Fulham's strikers continually running into offside positions, there was not much doing in the first half.
Neither side managed to create a decent chance in the opening half-hour as defences ruled the roost.
Newcastle's aerial strength made meat and drink of anything high sent into their area by Fulham's wide men Wayne Routledge and Simon Davies while Bocanegra was booked for pulling back Martins as the Nigerian striker executed a neat turn on the halfway line.
When Fulham tried to go through the middle they were just as ineffective; Moritz Volz was stopped dead in his tracks at the edge of the area by the powerful Onyewu's crunching tackle.
The German needed attention before he could carry on, and the home fans screamed for action as the American knocked lumps off the battling Helguson.
Newcastle carried hardly a threat, although Franck Queudrue did well to cut out James Milner's dangerous cross from the right after 35 minutes.
Fulham skipper Michael Brown went down clutching his face after a collision with Scott Parker but referee Phil Dowd was not fooled.
He gave a free-kick but ignored home fans' pleas to send off Parker for an elbow. Television replays suggested no contact at all.
There was, though, in the 41st minute when Stephen Carr tried foolishly to head the ball back to goalkeeper Steve Harper in a crowded United penalty area. Helguson so nearly nipped in first.
Just as the half was dying, Routledge was the nearest to a goal so far when he worked his way in from the left and skimmed the crossbar with his shot.
And almost immediately Newcastle went close when, following a corner, Jan Lastuvka - deputising in goal for Antti Niemi who was injured in the warm-up - parried Martins' shot and both Steve Taylor and Kieron Dyer had follow-up efforts blocked.
Although it was Newcastle who seemed faster out of the traps in the second half, it was Fulham who scored following a gift from Butt.
The midfielder, taking possession of Carr's routine throw-in, left a risky backpass dreadfully short in the 49th minute and Helguson seized the ball, sprinted between two flat-footed defenders and lofted a superb shot beyond Harper.
Instead of being stung into retaliation, Newcastle crumbled and were hit by a home barrage in which Simon Davies' header from a Liam Rosenior cross had to be splendidly tipped over by Harper.
McBride stood unmarked waiting for a Brown pass that never came after another battling Helguson run.
And Onyewu should have seen red instead of yellow for a deliberate tug on the Icelandic striker as he raced clean through on 69 minutes.
But McBride's clincher was only four minutes away, courtesy of a sweeping right-footed shot which brought his 11th goal of the season but owed everything to Diop's marvellous work, penetrating on the right to set him up perfectly.
Martins struck his 10th goal of the season from substitute Nolberto Solano's pass in the 92nd minute, but that was far too late.
Coleman salutes strikersFulham manager Chris Coleman saw his side hand out a second half drubbing to
Newcastle in a 2-1 win and saluted strikers Heidar Helguson and Brian McBride.
But he also admitted he had been given a major bonus in the return of Senegal
midfielder Papa Bouba Diop.
McBride, 34, struck his 11th goal of the season to clinch victory in the 73rd
minute after Helguson pounced on an error by Nicky Butt to grab the lead four
minutes after the break.
And Coleman said: 'I just wish McBride was five years younger. He showed
again what a great striker he is. And even though it was a big gift for our
first goal Heidar took it beautifully.'
McBride's strike however came courtesy of a brilliant run and cross by Diop
who should not have even been playing.
He was named as an emergency substitute when goalkeeper Antti Niemi, who had
been sidelined for a month with a neck injury before returning for the midweek
defeat at Sheffield United, damaged his lower back in the warm-up at Craven
Cottage.
With Jan Lastuvka promoted between the sticks, Fulham decided to go without a
keeper on the bench and named Diop, who has been frozen out of the side since
December 9 and was almost sold last week.
Wigan and Portsmouth were both interested in signing him and Coleman said:
'We had lots of calls about him but he wanted to stay and prove a point.
'He only went on because Moritz Volz was taking a battering but he did really
well for the second goal.
'There are not many around of his size (6ft 5in) and he is a big presence but
I've told him he has got to get back to his best and prove his commitment.
'He has to regain the form he showed in his first season here and recognise
that there are a lot of players giving him competition in midfield.'
Coleman added: 'The first half was not really an event but we matched
Newcastle all through and came into our own after the first goal. When that went
in it was all us.'
Newcastle and manager Glenn Roeder admitted: 'I think we gave a very flat
performance but what was most disappointing was the poor manner of the first
goal.
'Nicky Butt has been fantastic for us this season and I don't want to
criticise him for dropping a back-pass but goals change matches and what people
think about themselves.
'We probably had the best of what few chances there were in the first half
and I just said to the players at half-time to try to get through the first 10
minutes of the second half.
'But what was it? Three or four minutes and we are a goal behind.
'We couldn't come back after that but I'd never criticise the team for lack
of commitment. They all did their best but it just didn't happen for us
today.'
Roeder said he was impressed by the debut of his on-loan American centre back
Oguchi Oneywu and revealed: 'We've only had one training session with him since
he came in from Standard Liege and on that basis I thought he did very well.
'There is obviously more to come from him as there is from Obafemi Martins.
He had already scored 11 goals this season before his late one today and he is
settling in now.
'It is a lot different playing in Serie A than the Premier League and Oba has
been taking his time and is getting there now.
'He played up front on his own today with Kieron Dyer in the hole and when
Michael Owen and Shola Ameobi are fit to partner him I think you will see a lot
more.'