Andy Carroll scored twice in a Premier League away game for the first time in his career and Jonathan Calleri scored his first West Ham goal in a 3-1 win at Middlesbrough.
Carroll, who scored a stunning bicycle kick in the win over Crystal Palace last weekend, took the lead with a bullet header on nine minutes before firing the Hammers back ahead before half-time.
Cristhian Stuani had equalised for Boro, capping off a fine passing move, but the home side's second-half domination was undone at the death when Calleri came off the bench to add the away side's third.
In the absence of wantaway forward Dimitri Payet, West Ham have registered back-to-back Premier League wins but boss Slaven Bilic will worry after losing Mark Noble and Carroll to injury in the second half.
They should have taken the lead even earlier after a determined start presented Michail Antonio with a chance to tap home Aaron Cresswell's cross from all of six yards, but he missed the ball entirely.
Carroll, however, made no mistake when fixated on Cresswell's corner delivery and punted the opener into the left-hand corner.
West Ham had a sound case for a penalty when Noble was brought down in the box on 18 minutes and they were increasingly annoyed when Boro's resurgence yielded an equaliser on 27 minutes.
What they cannot grumble about was the quality of the move, with Negredo nodding down to the impressive Adama Traore, who fed in Calum Chambers to cross for Stuani at the back post.
Traore proved a nightmare to handle for West Ham's defenders, thriving on the right before switching to the left in the second half.
He orchestrated two further chances that Boro could have taken before half-time, first flashing a cross across goal himself before setting up Chambers for another delivery towards Negredo in the six-yard box.
But West Ham took the lead before the break when Antonio fired a wicked shot at Victor Valdes that the keeper could only parry in the path of Carroll, who slotted home despite suspicions of offside.
The Hammers lost Noble on 55 minutes after a hard challenge, and they immediately suffered with Boro gaining control in midfield and pressing with wave after wave of attacks.
But Aitor Karanka, who has signed two new strikers in Patrick Bamford and Rudy Gestede this month to try and arrest a baron spell in front of goal, watched as more chances went begging.
Marten de Roon forced Darren Randolph into a full-stretched save with a header but it was Gestede, brought in for £8m from Aston Villa, who had the best effort late on when he smacked a volley inches wide of the far post.
Bamford hustled and bustled but with so many players committed forward, the Hammers were able to break four on two deep into stoppage time and set-up Calleri, who has struggled since joining on loan from South America in the summer, to fire in via a deflection.
Middlesbrough: Valdes (6), Chambers (7), Bernardo (6), Gibson (7), Friend (6), Clayton (6), Forshaw (7), De Roon (6), Traore (8), Stuani (7), Negredo (7)
Subs used: Bamford (6), Gestede (6)
West Ham: Randolph (7); Byram (6), Reid (7), Ogbonna (6), Cresswell (7); Noble (7) Obiang (7); Feghouli (7), Lanzini (6), Antonio (8); Carroll (9)
Subs used: Collins (6), Calleri (7), Fernandes (7)
Man of the Match: Andy Carroll