Newcastle were deservedly beaten at the London Stadium as strikes from Lucas Paqueta, Tomas Soucek and a Sven Botman own goal helped the Hammers to a 3-1 victory.
Eddie Howe's side had taken the lead through Jacob Murphy inside four minutes, moments after Jarrod Bowen had struck the upright at the other end.
As the first half progressed, Newcastle looked increasingly likely to concede with Nick Pope called into action on several occasions.
Newcastle United go eight games without away win after latest defeat
The match officials looked favourably upon the Magpies, too, as a Video Assistant Referee intervention saw Rob Jones overturn his original decision to award a penalty kick to the home side after Malick Thiaw had felled Bowen inside the area.
While replays showed Thiaw got the faintest of touches on the ball before making contact with the England forward, the warning signs were there.
On the stroke of half-time, having been pegged back by Paqueta's equaliser, Botman turned the ball past his own goalkeeper to send the Hammers in at the break in front.
Howe made a triple change at the interval, bringing off Anthony Gordon, Nick Woltemade and Emil Krafth but the uncharacteristic trio of substitutions were unable to correct Newcastle's course in the match.
A late Soucek clincher ensured of all three points for the East Londoners and left Howe short of answers in his post-match press conference.
The Newcastle boss did not sugarcoat his assessment of the performance, describing it as being unlike the sort of display Newcastle have become renowned for over the past few seasons.
"I think just the body language, the collective spirit on the pitch, loads of little things that contribute to our performance, wasn't there.
"I don't think that was tactical. I don't think that was necessarily technical. It was a byproduct of us just not being where we needed to be mentally. And we did a lot of work with the players in between the last game to this. So it's a difficult one to work out right now," Howe said.
As for the positives, there were very few for Howe to focus on: "We'll go away and try and learn from today, because I think it's hopefully a turning point we can use for our advantage."
Newcastle are without an away win in the league since last season, now eight matches without such a result.
This term, the team have played five, drawn three and lost two on the road, scoring just twice and conceding five.
It is in stark contrast to the team's form at St. James' Park where they have picked up three league wins and were agonisingly close to earning points against Liverpool and Arsenal if not for stoppage time concessions.
