This was the 27-year-old’s maiden strike for the Hammers since arriving from Spanish side Valencia before the start of the season.
Feghouli smashed home into an empty net after Michail Antonio had rounded goalkeeper Wayne Hennessey to open the scoring in the 68th minute.
Although Andy Carroll’s stunning overhead kick was the highlight of the day as West Ham secured a valuable victory on Sam Allardyce's return to East London.
Manuel Lanzini secured the three points with a beautiful chip to plunge Palace deep into relegation zone as the Hammers walked away 3-0 winners.
Despite featuring recently in the 2018 World Cup Qualifiers for the Desert Warriors, Feghouli was a surprise exclusion with Algeria coach Georges Leekens citing his lack of game time as reason for the decision.
But with Dimitri Payet still forcing his way out of the struggling Hammers, Feghouli deputized in his absence and was flawless.
Can Feghouli fill Payet’s void permanently for West Ham?