Gary Cahill was the unlikely match-winner for Bolton as he produced a stunning strike in extra-time to beat West Ham 3-1 in their Carling Cup third-round tie at the Reebok Stadium.
The centre-back drilled home from 25 yards just six minutes into the additional period to turn things around for the home side with Johan Elmander sliding in a third very late on.
Wanderers captain Kevin Davies had struck with a header just before the end of 90 minutes to cancel out Herita Ilunga's first goal for the club on the hour.
Although the Premier League remains the priority for Bolton, the victory provided a welcome confidence boost after a sketchy start to the season.
For West Ham this was a seventh failure in eight years to reach the fourth round but at least manager Gianfranco Zola can concentrate on lifting his side away from the lower end of the league.