Brazilian giants Corinthians won the Club World Cup in Japan on Sunday, overcoming European champions Chelsea 1-0 in a closely-fought encounter.
Striker Guerrero got the goal as the Sao Paulo club secured their second intercontinental title - they won the FIFA Club World Championship in 2000.
"It's an incredible feeling," Guerrero told reporters after his goal sparked wild celebrations among the more than 15,000 travelling Brazilian fans among the crowd of 68,000.
"To win in front of so many Corinthians fans who came all this way. It's tremendous, unbelievable."
Interim Chelsea boss Rafael Benitez made three changes to the team that thrashed Mexican side Monterrey 3-1 in the semi-final - replacing Oscar, John Obi Mikel and Cesar Azpilicueta with Frank Lampard, Ramires and Victor Moses.
Corinthians coach Tite changed just one player from the side that scraped to a 1-0 last-four win over Egypt's Al Ahly, bringing in Jorge Henrique for Douglas.
The match at the 68,000-capacity International Stadium in Yokohama was frenetic right from the first whistle with both sides creating several chances as play swung from end to end.
Chelsea came closest to taking the lead after eight minutes when Corinthians goalkeeper Cassio fumbled a Gary Cahill effort from a corner, before gathering the ball just short of the goal-line as Victor Moses looked to pounce.
On 25 minutes the referee waved away a penalty appeal by Corinthians when centre-forward Guerrero went down softly under a challenge by Cahill.
Emerson should have scored three minutes later after Cahill let the ball slip under his foot. But the Corinthians forward blazed his shot over the bar from the edge of the penalty box with just Petr Cech to beat.
Guerrero then had a shot blocked shortly afterwards before striker Fernando Torres was similarly denied at the other end.
The Spaniard should have done better on 37 minutes however, expertly controlling a long-range pass from Lampard that split the Corinthians' defence. But a weak shot at Cassio meant the Brazilians breathed a sigh of relief.
Moses did better two minutes later, cutting in from the left and curling a shot which Cassio did well to tip round his left-hand post.
The Corinthians goalkeeper was proving tough to beat, holding onto a long-range shot from Juan Mata shortly afterwards, and the teams entered the break goalless.
The second half started as quick as the first, with Eden Hazard causing problems for the Corinthians defence before midfielder Paulinho gave Cech a fright with a shot that narrowly went wide on 64 minutes.
There was finally a breakthrough five minutes later when Guerrero headed in from close range after Danilo's shot was blocked.
Benitez brought Oscar on for Moses almost straightaway. But it was Torres who missed the best chance to equalise when he shot straight at the goalkeeper from the edge of the six-yard box with only four minutes to go.
Cahill was sent off shortly afterwards. Torres had the ball in the net in injury time, but it was ruled offside and Corinthians held on.
CONCACAF champions Monterrey took third place earlier Sunday, defeating Al Ahly 2-0 through goals from Jesus Corona and Cesar Delgado.