Alexandre Lacazette scored 21 seconds after coming off the bench to give Arsenal a hard-fought 1-0 win over Brighton.
The striker collected Bukayo Saka's cut-back with his first touch after replacing Gabriel Martinelli in the 66th minute at the Amex Stadium before composing himself and firing a clinical finish into the bottom corner.
The goal secured a second consecutive victory for Arsenal following their 3-1 win over Chelsea on Boxing Day, giving them back-to-back Premier League wins for the first time since their opening two games of the season.
- How the teams lined up | Match stats
- Premier League table | Fixtures | Results
- Get Sky Sports PL & Football for £18 a month
But they were made to work for it by Brighton, who dominated the first half and would have gone into the break in front had it not been for the wasteful finishing of Alireza Jahanbakhsh and Alexis Mac Allister.
Arsenal looked transformed in the second half, however, going close to scoring on numerous occasions before Lacazette broke the deadlock, his goal moving the Gunners from 15th to 13th in the table and pushing Brighton closer to the relegation zone.
How Arsenal clinched another win
Mikel Arteta stuck with the young players who impressed against Chelsea as Martinelli, Saka and Emile Smith Rowe kept their places in the side, the only change seeing Pierre-Emerick Aubameyang replace Lacazette following his return from a calf injury.
Arsenal started the game confidently enough, but for all their improvement against Chelsea, there was a familiar lack of attacking thrust in the first half, with Aubameyang cutting an isolated figure.
Arsenal: Leno (7), Bellerin (7), Holding (7), Mari (7), Tierney (7), Elneny (6), Xhaka (7), Smith Rowe (7), Martinelli (6), Saka (8), Aubameyang (6).
Subs: Lacazette (7), Ceballos (6), Maitland-Niles (6).
Chelsea: Sanchez (7), Veltman (6), Webster (7), Dunk (6), Burn (6), Bernardo (6), Bissouma (8), Gross (6), Propper (6), Mac Allister (6), Jahanbakhsh (6).
Subs: Maupay (6), March (6), Trossard (6).
Man of the Match: Bukayo Saka.
Brighton had a day less to recover for the game following their 2-2 draw with West Ham on Sunday, forcing Graham Potter to make six changes to his team, but they looked the more dangerous side before the break despite their quick turnaround.
Their best chances fell to Jahanbakhsh and Mac Allister, both of whom fired over when they should have hit the target after Mohamed Elneny lost possession near his own box on two separate occasions.
Bernd Leno then denied Jahanbakhsh when he fired a low effort towards goal from a diagonal angle, and half-time arrived with Brighton having had eight shots to Arsenal's one - a free-kick from Granit Xhaka which sailed harmlessly over.
- Arsenal's only change from the 3-1 win over Chelsea saw Pierre-Emerick Aubameyang return in place of Alexandre Lacazette.
- Brighton made six changes from the 2-2 draw against West Ham with Danny Welbeck and Neal Maupay among those to drop to the bench.
The Gunners were fortunate not to be punished for their poor showing in that half but Arteta's team talk had an immediate impact as they created a flurry of chances after the break.
The first saw Aubameyang meet a cross from the outstanding Saka with a first-time effort from six yards out which was smartly saved by Brighton goalkeeper Robert Sanchez.
Martinelli was next to go close, firing narrowly over the bar following an excellent piece of skill from Smith Rowe, and shortly after that Aubameyang spurned another opportunity when he curled a shot wide from another Smith Rowe pass.
It took Lacazette's introduction for the breakthrough to arrive.
The assist from Saka was superb, the youngster speeding away from Dan Burn before picking out his unmarked team-mate, who had time and space to dispatch his finish as he found the net for the third successive game.
Brighton tried to rally in the closing stages, but they never came close to testing Leno, with Joel Veltman blasting high and wide from their best opening seven minutes from time.
For Arsenal, this was not a fluent victory like the one over Chelsea, but it was an important one nonetheless as they attempt to turn a corner following their dismal start to the season.
The only dampener on their evening was an apparent injury to Saka, who hobbled off to be replaced by Dani Ceballos in the 81st minute.
While Arsenal are looking up again, Brighton remain in a perilous position, just two points above the relegation zone with only one win from their last 14 Premier League games.
Man of the match - Bukayo Saka
The sight of Bukayo Saka receiving treatment for an injury in the closing stages of the game will have had Arsenal supporters shifting uncomfortably in their seats. The 19-year-old is fast becoming their most influential player.
He followed up his man-of-the-match showing against Chelsea with another performance brimming with quality at the Amex Stadium.
The youngster's assist for Lacazette's winner was outstanding but it was just one of many examples of him running fearlessly at the Brighton defence. He created more chances than anyone else on the pitch from Arsenal's right flank, with Brighton often finding that fouling him was the only way to stop him.
Mikel Arteta will hope he avoids serious injury, because no player has been more important in Arsenal's mini-resurgence of late.
What the managers said
Brighton's Graham Potter: "Chances wise, I thought it was quite even. We had some good ones in the first half, they had some better ones second half.
"A little moment of quality has undone us but I thought it was quite an even game. Performance-wise, we were OK.
"If you don't score and they do that's how it is, I thought it was quite an even game, there weren't too many chances for them or us. Our work rate was really, really good.
"We're suffering a bit but we need to deal with it and move forward."
Arsenal's Mikel Arteta: "The fact we won against Chelsea was a big boost and to come here three days later and get another win for us is massively important. I'm proud of the boys and happy with the result.
"When you lose the amount of games that we did recently, to maintain high spirits is a big challenge. But we have managed to do that.
"The best medicine is wins. The picture looks much better at the moment. We just need to have that consistency go against West Brom now and try to win again."
Opta stats: Brighton's dismal year at home
- Brighton end 2020 with just one Premier League home win (17 games), the lowest total of victories on home soil in a calendar year in the history of the competition (excluding promoted/relegated teams).
- Brighton have won just one of their last 14 Premier League games, drawing seven and losing six.
- Arsenal have won back-to-back league games this season for the first time since their opening two games back in September.
- Arsenal kept their fourth away clean sheet this season in the Premier League, a figure only Aston Villa can better in 2020-21 (five).
- Alexandre Lacazette has scored in each of his last three games for Arsenal in all competitions, after netting just once in his previous 12.
- Since the start of last season, Bukayo Saka has registered 15 assists in all competitions for Arsenal, more than any other player for the club.
Arsenal continue their Premier League campaign away to West Brom on Saturday, January 2, with kick-off at 8pm. Brighton host Wolves on the same day, live on Sky Sports Premier League HD from 5pm, with kick-off at 5.30pm.