WEST HAM 2 NEWCASTLE 3
Elliot, Yedlin, Lascelles, Clark, Manquillo, Ritchie, Saivet (Mbemba 84'), Diamé, Atsu (Murphy 90+1'), Gayle (Pérez 76'), Joselu
Subs: Dummett, Aarons, Haidara, Darlow
In an eventful match at London Stadium, Senegalese midfielder Henri Saivet played a big role in two goals inside the first 10 minutes.
First, his loose pass was picked up by Hammers forward Marko Arnautovic, who raced into the area before slotting past Rob Elliot.
That lead lasted only four minutes as Saivet - making his first league start under Benitez - atoned for his error with a 25-yard free-kick that sneaked inside Adrian's near post.
The visitors hit the woodwork twice before they went in front, when Mo Diame fired in from Christian Atsu's pass.
But they almost ceded their lead immediately - the Hammers winning a penalty when Michail Antonio was brought down by Ciaran Clark, only for Elliot to save Andre Ayew's low effort.
Atsu soon made it 3-1 with a poked finish after a swift break, but David Moyes' side gave themselves more than a fighting chance when Ayew smashed home after Andy Carroll's header was parried.
Newcastle survived a frantic closing spell to secure a victory that brought relief for the travelling fans.
Benitez made five changes to the starting line-up, including bringing in Saivet and Diame. Bar the early mistake from Saivet, the core of the midfield looked solid against a team missing the injured Mark Noble.
It was on the wings that Newcastle had the most joy, though, with the recalled Matt Ritchie and DeAndre Yedlin a constant thorn on the right, and Atsu producing an assist and a goal from the other side.
More performances like this could make their recent heartaches a distant memory.
As for the Hammers, had Ayew scored his penalty, things could have ended differently. The Ghana midfielder appeared to lack conviction when he struck the ball as Elliot guessed the right way.
One player who had plenty of conviction was ex-Newcastle striker Andy Carroll. After coming on as a substitute the 6ft 4in forward dragged two defenders everywhere he went, but not even that could prevent him from getting on the end of a corner which resulted in Ayew pulling it back to 3-2.
However, that was one of only a few good deliveries that reached the Geordie as West Ham opted to launch the ball up to striker as the clock ticked down.
Moyes' side slip to 17th, a point above the relegation zone, after their first defeat in four.