Lacazette flicked in a finish from Emile Smith-Rowe's cross and headed home his second in the friendly.
Mesut Ozil, who quit international football after the World Cup, captained the Gunners and stroked in the opener, while Rob Holding headed in the fourth and Eddie Nketiah scored the fifth.
Christopher Nkunku had briefly levelled for PSG with a second-half penalty.
The spot-kick was awarded after Sead Kolasinac tripped Timothy Weah in the box, but Arsenal ran away with the game thereafter.
New Gunners manager Unai Emery had said he wants "five captains" in his team this season and handed the armband to midfielder Ozil on this occasion.
Ozil cited "racism and disrespect" over his Turkish roots in his decision to call time on his Germany career but repaid his club manager's faith by converting from Pierre Emerick-Aubameyang's cutback.
Ozil was one of five players replaced just after the hour mark, and two of those coming on - French striker Lacazette and English defender Holding - both found the net, as did Nketiah with a cool strike late on.
Lacazette said: "This can give us some confidence and we need this after last season and we are happy after scoring five goals today."
Veteran Italian goalkeeper Gianluigi Buffon started the game for Ligue 1 champions PSG after joining in the summer from Serie A winners Juventus, and the 40-year-old reacted sharply to deny Alex Iwobi and Aubameyang.
Arsenal will continue their pre-season campaign against London rivals Chelsea in Dublin on Wednesday.
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