Kai Havertz scored a penalty deep into extra time as Chelsea defeated Palmeiras 2-1 in the Club World Cup final on Saturday to complete their collection of major trophies.
Romelu Lukaku's superb header gave the European champions the lead on 54 minutes but Raphael Veiga levelled from the spot for the Copa Libertadores winners just past the hour in Abu Dhabi.
Havertz, the hero in the Champions League final against Manchester City, was Chelsea's match-winner again as he converted a penalty on 117 minutes awarded following a VAR review.
Chelsea have now claimed every possible trophy since Roman Abramovich bought the club in 2003, and become the third English side to win the global tournament after Manchester United and Liverpool.
The Blues avenged their 1-0 loss to Corinthians in 2012 final, but will have little time to celebrate with a critical stretch on the horizon once they return to London.
They face Lille in the Champions League last 16 either side of the League Cup final against Liverpool and FA Cup fifths round, playing in four different competitions in 12 days.
Chelsea coach Thomas Tuchel was back in the dugout having flown out to Abu Dhabi on Friday after missing the past two games following a positive test for Covid-19.
Edouard Mendy returned in goal in the wake of Senegal's Africa Cup of Nations victory, at the expense of Kepa Arrizabalaga, whose much improved form is likely to attract interest from other clubs in the summer.
Chelsea's decline in the Premier League has coincided with lack of authority and conviction, and despite controlling possession it wasn't until the end of the first half they forced Weverton into a save.
Even then, Thiago Silva's searing drive from distance appeared to be going wide.
In contrast, Palmeiras were twice left to rue their lack of efficiency as Dudu stabbed well wide before Andreas Christensen made a key intervention to negate a promising attack for the Brazilians.