The Gunners returned to the competition for the first time since 2017 and made a statement with an emphatic result over the Dutch giants.
Saka opened the scoring in the eighth minute, combining with captain Martin Odegaard before finding the back of the net.
The PFA Young Player of the Year has carried his electric form from the 2022/23 season into the new campaign.
He bagged 14 goals and 11 assists last season as Arsenal pushed Manchester City for the Premier League title.
The Hale End Academy graduate has started this season well, with two goals and two assists in five league games.
Saka turned provider moments later as Arsenal’s front three combined for the second against PSV.
Gabriel Jesus brought the ball forward in transition before releasing the England international, who set up Leandro Trossard to find the back of the net with a fine finish.
Arsenal had control of the game and made it three before the half-time whistle.
Trossard crossed for Jesus, and the Brazilian international controlled the ball expertly before unleashing a vicious hit beyond PSV’s Walter Benitez.
Arsenal saw out the victory as Odegaard netted a fourth to give them the lead in Group B ahead of Lens and Sevilla.
The Gunners will hope to consolidate their lead in the group when they face Lens on October 3 who are fighting at the bottom of the table after a poor start to the season.
Arsenal play Tottenham Hotspur in the Premier League this weekend.
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