Danny Ings' first goals for West Ham proved the launching pad for a huge 4-0 win as David Moyes' side pulled themselves out of the Premier League relegation zone.
Ings, a 15m signing from Aston Villa in January, proved the difference with two identical goals in three second-half minutes as the Hammers capped a much-improved display with a potentially significant three points.
The former Liverpool and Burnley striker was quiet for large periods but his clinical finishes settled the nerves around London Stadium and ensured that the hosts could kick on to an eventual thumping victory.
Further goals from captain Declan Rice and substitute Michail Antonio sent the home fans away smiling on a rare goal-filled afternoon.
Forest, who have only managed three goals away from home all campaign, were lifeless throughout in a disappointing display.