West Brom enjoyed their first league win in six games to ease their relegation fears but deepen Newcastle's worries at the bottom of the table.
Both teams hit the crossbar, with Paul Dummett's header ricocheting off the woodwork for Newcastle and Victor Anichebe going close for the hosts.
Just as a draw seemed inevitable, Darren Fletcher timed his run perfectly to head home Claudio Yacob's cross.
But it was poor goalkeeping as Karl Darlow should have done better.
Darlow will look back on his Premier League debut with mixed emotions. He was a late inclusion in Steve McClaren's line up as regular goalkeeper Rob Elliot was withdrawn before kick-off because of illness.
The 25-year-old, whose only previous appearance for the Magpies was in the Capital One Cup against Northampton, was uncertain under the high ball throughout and should have held on to Fletcher's header, rather than allowing it to slip through his hands with 12 minutes remaining.
It will leave United fans wondering whether their team, who remain in the bottom three, two points adrift of safety, would have earned a point had someone of Elliot's experience been on the pitch.
Ironically, Darlow's best contribution came after conceding, acrobatically diving towards his near post to stop substitute Saido Berahino's goal-bound effort.
Baggies boss Tony Pulis had warned of a "concertina" effect after two successive defeats against two of the teams below them - Bournemouth and Swansea - but the alarm bells will have dimmed a little after this hard-earned win which moves them six points off the relegation zone.
Despite his team dominating possession and looking the stronger side in the second half, it looked as if the Baggies' poor home form would continue - they had only earned eight points at The Hawthorns prior to this match - until Fletcher struck for his 20th league goal.
Scoring has been a problem for Pulis' men of late, but Victor Anichebe - making his first start of the season - added ballast to West Brom's forward line and was a nuisance and a reliable outlet.
His performance was only missing a goal, the crossbar preventing him from heading home from a corner. In the first half, Dummett also blocked Anichebe's powerful effort and the industrious striker received a deserved ovation from the home fans as he hobbled off injured before full-time.
Newcastle boss Steve McClaren said it had been a tough three days for his team, who have now endured two narrow defeats over the Christmas period.
But the Magpies' spirit did not appear to be damaged by the Boxing Day defeat which saw Everton score with the last kick of the ball.
McClaren's men courageously defended against West Brom's direct approach (the Baggies had 17 corners and 22 shots on goal), with Fabricio Coloccini particularly impressive.
The ubiquitous Newcastle captain cleared James Morrison's effort off the line in the opening minutes and had an improvised backheel - after Dummett's header had struck the crossbar - saved by Boaz Myhill.
McClaren said his team should have had a second-half penalty when the score was goalless and the evidence supports his claim, as Jonny Evans appeared to grab Aleksandar Mitrovic around the midriff as the striker aimed to shoot from six yards.
More to follow.
Full Time Match ends, West Bromwich Albion 1, Newcastle United 0.
90:00 +4:14 Full timeFull Time Second Half ends, West Bromwich Albion 1, Newcastle United 0.
90:00 +3:51Corner, West Bromwich Albion. Conceded by Chancel Mbemba.
90:00 +2:10Stéphane Sessegnon (West Bromwich Albion) wins a free kick on the right wing.
90:00 +2:10Foul by Paul Dummett (Newcastle United).
90:00 +0:18Delay over. They are ready to continue.
89:06Delay in match Moussa Sissoko (Newcastle United) because of an injury.
88:02Attempt blocked. Craig Dawson (West Bromwich Albion) header from the left side of the six yard box is blocked. Assisted by Stéphane Sessegnon with a cross.
87:35Delay over. They are ready to continue.
87:32 SubstitutionSubstitution Substitution, West Bromwich Albion. Rickie Lambert replaces Victor Anichebe because of an injury.
86:40Delay in match Victor Anichebe (West Bromwich Albion) because of an injury.
86:07Corner, West Bromwich Albion. Conceded by Karl Darlow.
86:05Attempt saved. Saido Berahino (West Bromwich Albion) left footed shot from the left side of the box is saved in the top left corner. Assisted by Stéphane Sessegnon.
85:33Foul by Claudio Yacob (West Bromwich Albion).
85:33Florian Thauvin (Newcastle United) wins a free kick in the defensive half.
85:07 SubstitutionSubstitution Substitution, Newcastle United. Florian Thauvin replaces Jack Colback.
83:37Saido Berahino (West Bromwich Albion) wins a free kick on the right wing.
83:37Foul by Fabricio Coloccini (Newcastle United).
81:31Corner, West Bromwich Albion. Conceded by Karl Darlow.
81:26Attempt saved. Victor Anichebe (West Bromwich Albion) left footed shot from the centre of the box is saved in the bottom left corner. Assisted by Jonny Evans with a through ball.
Corner, West Bromwich Albion. Conceded by Fabricio Coloccini.
77:51 Goal scoredGoal! Goal! West Bromwich Albion 1, Newcastle United 0. Darren Fletcher (West Bromwich Albion) header from the centre of the box to the bottom right corner. Assisted by Claudio Yacob with a cross.
77:38Attempt blocked. Saido Berahino (West Bromwich Albion) left footed shot from the right side of the box is blocked. Assisted by Stéphane Sessegnon.
76:29Corner, West Bromwich Albion. Conceded by Paul Dummett.
75:01Stéphane Sessegnon (West Bromwich Albion) wins a free kick in the defensive half.
75:01Foul by Moussa Sissoko (Newcastle United).
74:23Attempt blocked. Jonny Evans (West Bromwich Albion) left footed shot from very close range is blocked.
74:21Attempt blocked. Jonny Evans (West Bromwich Albion) right footed shot from very close range is blocked.
74:20Victor Anichebe (West Bromwich Albion) hits the bar with a header from very close range. Assisted by Stéphane Sessegnon with a cross following a corner.
73:53Corner, West Bromwich Albion. Conceded by Karl Darlow.
73:42Jonny Evans (West Bromwich Albion) wins a free kick in the defensive half.
73:42Foul by Aleksandar Mitrovic (Newcastle United).
72:19Offside, West Bromwich Albion. Boaz Myhill tries a through ball, but Victor Anichebe is caught offside.
71:48 SubstitutionSubstitution Substitution, Newcastle United. Siem de Jong replaces Ayoze Pérez.
69:50 SubstitutionSubstitution Substitution, West Bromwich Albion. Saido Berahino replaces James Morrison.
66:45Delay over. They are ready to continue.
65:35Delay in match Paul Dummett (Newcastle United) because of an injury.
64:45Victor Anichebe (West Bromwich Albion) wins a free kick in the attacking half.
64:45Foul by Cheick Tioté (Newcastle United).
64:31Attempt saved. Aleksandar Mitrovic (Newcastle United) right footed shot from the right side of the box is saved in the centre of the goal. Assisted by Ayoze Pérez.
61:47Attempt missed. Ayoze Pérez (Newcastle United) right footed shot from the left side of the box misses to the right following a corner.
60:23Corner, Newcastle United. Conceded by Chris Brunt.
60:22Attempt blocked. Aleksandar Mitrovic (Newcastle United) right footed shot from the centre of the box is blocked. Assisted by Ayoze Pérez.
59:07Corner, West Bromwich Albion. Conceded by Paul Dummett.
58:13Gareth McAuley (West Bromwich Albion) wins a free kick in the defensive half.
58:13Foul by Aleksandar Mitrovic (Newcastle United).
55:12Corner, Newcastle United. Conceded by Jonny Evans.
54:16Corner, Newcastle United. Conceded by Chris Brunt.
54:10Paul Dummett (Newcastle United) hits the bar with a header from very close range. Assisted by Ayoze Pérez with a cross following a corner.
53:36Corner, Newcastle United. Conceded by Craig Dawson.
51:55Foul by Stéphane Sessegnon (West Bromwich Albion).
51:55Paul Dummett (Newcastle United) wins a free kick in the defensive half.
49:18Stéphane Sessegnon (West Bromwich Albion) wins a free kick on the right wing.
49:18Foul by Aleksandar Mitrovic (Newcastle United).
49:10Attempt blocked. Craig Dawson (West Bromwich Albion) right footed shot from the centre of the box is blocked. Assisted by Gareth McAuley.
48:20Corner, West Bromwich Albion. Conceded by Georginio Wijnaldum.
45:46Offside, West Bromwich Albion. Gareth McAuley tries a through ball, but Victor Anichebe is caught offside.
45:09Hand ball by Moussa Sissoko (Newcastle United).
45:00Second Half begins West Bromwich Albion 0, Newcastle United 0.
45:00 +2:46 Half timeHalf Time First Half ends, West Bromwich Albion 0, Newcastle United 0.
45:00 +1:56Corner, West Bromwich Albion. Conceded by Ayoze Pérez.
45:00 +1:52Attempt blocked. Craig Gardner (West Bromwich Albion) right footed shot from outside the box is blocked.
45:00 +0:46Stéphane Sessegnon (West Bromwich Albion) wins a free kick in the attacking half.
45:00 +0:46Foul by Jack Colback (Newcastle United).
42:10Attempt missed. Claudio Yacob (West Bromwich Albion) left footed shot from outside the box misses to the right. Assisted by Darren Fletcher.
39:51Attempt missed. Darren Fletcher (West Bromwich Albion) right footed shot from the centre of the box is too high following a set piece situation.
39:49Attempt blocked. Darren Fletcher (West Bromwich Albion) right footed shot from the centre of the box is blocked.
39:13Victor Anichebe (West Bromwich Albion) wins a free kick in the attacking half.
39:13Foul by Cheick Tioté (Newcastle United).
38:36Corner, Newcastle United. Conceded by Craig Dawson.
36:45Attempt blocked. Darren Fletcher (West Bromwich Albion) right footed shot from outside the box is blocked. Assisted by Stéphane Sessegnon.
35:28Corner, West Bromwich Albion. Conceded by Moussa Sissoko.
34:58Corner, West Bromwich Albion. Conceded by Chancel Mbemba.
34:11Corner, West Bromwich Albion. Conceded by Karl Darlow.
33:28Foul by Gareth McAuley (West Bromwich Albion).
33:28Aleksandar Mitrovic (Newcastle United) wins a free kick in the defensive half.
32:04Foul by Craig Gardner (West Bromwich Albion).
32:04Moussa Sissoko (Newcastle United) wins a free kick in the defensive half.
31:34Claudio Yacob (West Bromwich Albion) wins a free kick in the defensive half.
31:34Foul by Aleksandar Mitrovic (Newcastle United).
30:26Attempt missed. Chris Brunt (West Bromwich Albion) right footed shot from the right side of the box is high and wide to the right. Assisted by Jonny Evans with a cross.
29:46Corner, West Bromwich Albion. Conceded by Paul Dummett.
29:02Victor Anichebe (West Bromwich Albion) wins a free kick in the attacking half.
29:02Foul by Paul Dummett (Newcastle United).
27:46Attempt blocked. Darren Fletcher (West Bromwich Albion) right footed shot from the centre of the box is blocked. Assisted by James Morrison with a cross.
26:21 SubstitutionSubstitution Substitution, Newcastle United. Cheick Tioté replaces Vurnon Anita because of an injury.
25:16Delay over. They are ready to continue.
23:54Delay in match Vurnon Anita (Newcastle United) because of an injury.
23:19Foul by Victor Anichebe (West Bromwich Albion).
23:19Vurnon Anita (Newcastle United) wins a free kick in the defensive half.
21:56Attempt missed. James Morrison (West Bromwich Albion) right footed shot from outside the box misses to the right. Assisted by Craig Gardner.
20:08Corner, Newcastle United. Conceded by Gareth McAuley.
20:07Attempt blocked. Aleksandar Mitrovic (Newcastle United) left footed shot from the centre of the box is blocked. Assisted by Georginio Wijnaldum with a cross.
18:05Attempt missed. Ayoze Pérez (Newcastle United) right footed shot from the left side of the box is close, but misses the top right corner. Assisted by Georginio Wijnaldum.
17:09 SubstitutionSubstitution Substitution, West Bromwich Albion. Craig Gardner replaces Jonas Olsson because of an injury.
16:58Delay over. They are ready to continue.
16:25Delay in match Jonas Olsson (West Bromwich Albion) because of an injury.
14:20Corner, West Bromwich Albion. Conceded by Fabricio Coloccini.
12:37Attempt saved. Georginio Wijnaldum (Newcastle United) right footed shot from the right side of the box is saved in the bottom right corner. Assisted by Ayoze Pérez.
11:36Stéphane Sessegnon (West Bromwich Albion) wins a free kick in the defensive half.
11:36Foul by Paul Dummett (Newcastle United).
10:19Corner, West Bromwich Albion. Conceded by Daryl Janmaat.
9:57Attempt saved. James Morrison (West Bromwich Albion) right footed shot from outside the box is saved in the centre of the goal. Assisted by Victor Anichebe.
9:53Attempt blocked. Victor Anichebe (West Bromwich Albion) right footed shot from the centre of the box is blocked. Assisted by Craig Dawson.
9:12Corner, West Bromwich Albion. Conceded by Aleksandar Mitrovic.
8:35Corner, West Bromwich Albion. Conceded by Paul Dummett.
8:30Attempt blocked. Victor Anichebe (West Bromwich Albion) right footed shot from the centre of the box is blocked. Assisted by Darren Fletcher.
6:18Foul by Jonny Evans (West Bromwich Albion).
6:18Aleksandar Mitrovic (Newcastle United) wins a free kick in the defensive half.
3:21Foul by Stéphane Sessegnon (West Bromwich Albion).
3:21Georginio Wijnaldum (Newcastle United) wins a free kick in the defensive half.
2:31Attempt blocked. James Morrison (West Bromwich Albion) right footed shot from the centre of the box is blocked.
2:30Attempt blocked. Victor Anichebe (West Bromwich Albion) left footed shot from the centre of the box is blocked. Assisted by Chris Brunt.
2:03Corner, West Bromwich Albion. Conceded by Chancel Mbemba.
0:53Offside, Newcastle United. Paul Dummett tries a through ball, but Aleksandar Mitrovic is caught offside.
0:00First Half begins.
0:00Lineups are announced and players are warming up.
Live data and text provided by our data suppliers