Brighton's dazzling display was highlighted by Mitoma's stunning opener. The Japanese winger brought down a long ball from Bart Verbruggen with an exquisite touch before slotting it into the bottom corner, leaving Chelsea's defense in disarray.
Enzo Maresca, Chelsea's manager, reflected on the match, "Probably since I arrived that is the worst performance, especially in the moment we are in. We are fourth in the league and winning tonight you could go one point from third and make the gap to the rest bigger.
"The performance is not one you want to offer, so we are very upset and sorry for the fans that were here."
The Seagulls capitalized further when Minteh scored twice. His first came after a swift move involving Danny Welbeck, where he outmaneuvered Marc Cucurella to score.
His second was a result of good teamwork with Welbeck again, finishing with a shot that deflected off Trevoh Chalobah past goalkeeper Filip Jorgensen.
Brighton's manager Fabian Hurzeler was effusive in his praise, "I wouldn't say it was complete, we suffered at the start and then after the first goal we got slightly too passive. But we defended quite well, and that was the key today. Compactness, intensity, and always doing it together."
He also lauded Mitoma's contribution, "Sometimes you can't explain the things from special players. It was a special action from him, and he deserves it because he works hard every day."
For Chelsea, the night was marked by frustrations. Cole Palmer missed early chances, and Noni Madueke was forced off injured early in the game.
The defeat extends Chelsea's poor run of form away from home, with only two wins from their last eight league matches since Boxing Day.
This loss against Brighton, following their recent FA Cup exit to the same opposition, underscores the challenges Chelsea face, particularly with injuries in the squad. Maresca noted, "It is difficult when you don't have a proper number nine. So you always have to find a different solution. In the last third, we struggled doing things that until a week or two ago we were doing well."
Brighton, on the other hand, celebrated ending their five-game winless home streak in the Premier League, with this victory showcasing their potential to challenge higher up the table.