The Brazilian gave Barcelona an early advantage with a superb individual finish before Karim Adeyemi doubled the lead with a stunning long-range strike. Raphinha then added another after the break, with Lamine Yamal and substitute Gabriel Jesus completing a convincing victory.
Raphinha's performance came just days after his surprise omission from the 30-player Ballon d'Or shortlist. The forward responded in emphatic fashion, taking his tally to eight goals in six appearances this season after adapting to a more central role following Barcelona's summer departures in attack.
His first arrived after only three minutes. Raphinha burst into the penalty area, cut inside two defenders and calmly finished on a rain-soaked pitch to put the hosts ahead.
Feyenoord briefly threatened to respond, with Anis Hadj Moussa denied by Joan Garcia after the visitors had also seen penalty appeals rejected. Barcelona soon regained control, with Adeyemi curling a superb effort into the top corner from outside the area.
The home side continued to create chances, and Joao Cancelo struck the outside of the post before Raphinha put the result beyond doubt in the 57th minute. Pedri's perfectly weighted pass released him behind the defence, allowing the Brazilian to fire beyond Tjark Ernst.
Barcelona's dominance continued as Yamal added a fourth from a free-kick in the 77th minute, although they were denied a clean sheet when Sem Steijn pulled one back eight minutes later.
There was still time for another highlight as Gabriel Jesus, introduced from the bench, headed home Yamal's cross for his first Barcelona goal since completing his move from Arsenal.
The result extended Barcelona's perfect start to the campaign, with Flick's side winning all five of their matches and scoring five goals in four of them. However, the Catalan club's wait for a Champions League clean sheet continues, with their last in the competition dating back to April 2025.
Barcelona midfielder Rodri has apologised to Valencia after comments he made from the substitutes' bench during Barcelona's 5-0 victory at Mestalla were caught on camera.
Hansi Flick has backed Lamine Yamal to win the 2026 Ballon d'Or after Barcelona produced another impressive attacking display in their 5-1 Champions League victory over Feyenoord at Camp Nou on Wednesday.
Gabriel Jesus has revealed he was unexpectedly separated from Arsenal's first-team squad during the final stages of his time at the club before securing a move to Barcelona.
Serie A champions Napoli will be without last year's player of the season Scott McTominay for Wednesday's Champions League opener against Arsenal as the former Manchester United midfielder has undergone heart surgery.
