Cambiasso netted with a sweet strike in the 12th minute, hitting the ball first time from just outside the box after it had sat up for him from a ricochet.
West Ham almost found themselves 2-0 down but goalkeeper Adrian coming to their rescue by saving David Nugent’s 15th-minute penalty.
Leicester’s win was sealed by substitute Andy King’s late tap-in, following Cheikhou Kouyate’s equaliser around the half-hour. It was Leicester’s first win in nine league matches, leaving them just four points from safety with eight games left to play.
Pearson said of 34-year-old former Real Madrid, Inter Milan and Argentina player Cambiasso: “Even if he hadn’t scored, I would still have said he was man of the match.
“Success for him at Leicester this year will be to be instrumental in us avoiding relegation. Hopefully he will be a success at that as well.”
Schmeichel, de Laet (King 79), Huth, Morgan, Schlupp, James, Cambiasso, Mahrez (Albrighton 45), Nugent, Vardy, Ulloa (Kramaric 72)
Adrián, Jenkinson, Collins, Reid, Cresswell, Noble 30 Song (de Carvalho 88), Kouyaté, Downing, Nolan (Amalfitano 65), Sakho (Cole 80)