Pierre-Emerick Aubameyang made an unexpected start against his former club, but was substituted before halftime after only nine touches on the ball, with Kai Havertz leading the line instead.
Chelsea showed signs of improvement after the break. On 65 minutes, Noni Madueke scored his first Chelsea goal with a sloppy finish from Mateo Kovacic's through-ball.
Arsenal had an injury scare near the end when defender Gabriel Magalhaes walked out with what appeared to be a muscular ailment.
Chelsea's interim manager Frank Lampard has now lost all six of his games in charge, while Arsenal has reclaimed first place in the Premier League by two points after playing two more games than Manchester City.
Arsenal's morale was damaged after four losses, and Manchester City moved into first place in the Premier League standings. As a result, they were a weak team at kickoff today.
In those four defeats, Liverpool, West Ham, Southampton, and Manchester City all had reasons to cheer, whether it was chasing Champions League qualification, avoiding relegation, or attempting to win the league.
But Chelsea, managerless and dissatisfied in mid-table, had nothing to bring them together other than caretaker manager Frank Lampard's demand for a show of pride in a London derby. That rallying cry fell on deaf ears.
Chelsea were almost incomprehensibly poor here at the Emirates, allowing the Gunners to rediscover their stride after a difficult start.