Arsenal scored two first-half goals to beat north London rivals Tottenham for the first time in seven Premier League games.
Defender Shkodran Mustafi looped home a header from Mesut Ozil's cross, but Spurs may well feel the free-kick awarded for Davinson Sanchez's foul on Alexis Sanchez was a harsh decision.
The Gunners doubled their lead just five minutes later, as Chilean Sanchez lashed in from close range following Alexandre Lacazette's cutback. Sanchez could have added a third but his shot was pushed away by Hugo Lloris.
The visitors' best opportunity fell to midfielder Christian Eriksen in the first half, but the Dane's low shot struck the post, and Petr Cech made a full-stretch save to keep out Eric Dier's header.
Spurs striker Harry Kane, who looked short of fitness with his right leg heavily strapped, dragged a shot wide from the edge of the box and had an effort blocked from eight yards out.
Both Kane and midfielder Dele Alli missed England's two friendlies during the international break through injury and were replaced with 15 minutes to go, substitutions well received by the home supporters at Emirates Stadium.
Arsene Wenger's Arsenal move up to fifth in the table, one point behind Mauricio Pochettino's side.