An early Ivan Ramis volley and second half strike from James McArthur sealed a priceless home victory for Wigan Athletic, despite conceding to a late James Tomkins header.
The game flowed for Roberto Martinez's side and the counter attacking football wowed the crowd.
Martinez lined up with the same team that traveled to South Wales last week but, this time they had a spring in their step from the off.
The game had barely got underway when Latics took the lead as Jean Beausejour's excellent work down the left won a corner.
The Chilean was the man to deliver the set piece and unlikely hero Ramis was on hand to smash in a spectacular left foot volley.
He poised himself on the penalty spot and with exquisite technique the ball just flew past a helpless Jussi Jaaskelainen.
Taking the lead so early gave Latics a sense of confidence and everything West Ham tried was countered as the home side searched for more goals.
A minute after half time there was another crucially timed goal when Jaaskelainen fluffed his lines and played the ball to Beausejour 30 yards out.
Di Santo received the pass from the centre out on the left before laying the ball back to Beausejour.
His clipped pass towards Shaun Maloney in the six yard box was knocked down and into the path of McArthur who drove the ball low and left of the keeper to make it 2-0 on just 46 minutes.
Arouna Kone and Franco di Santo carried Latics forward on many occasions with their tireless running but, it was the hard work of James McCarthy and McArthur that impressed the most as they constantly broke up play in the middle.
West Ham rarely threatened but pushed hard towards the end.
First Jame Tomkins rattled the bar as he got loose of his marker at the back post, and then came the equaliser as Tomkins again lost his man but this time volleyed in first time to grab a consolation goal.