Mariona Caldentey, Alexia Putellas, Asisat Oshoala and Lieke Martens were all on target as the formidable and prolific LaLiga champions made a fine start to the new 16-team group stage in a match that pitted two of Europe’s most in-form teams against each other.
It was one-way traffic from the outset at the Johan Cruyff Stadium, with the quartet of Putellas, Caroline Graham Hansen, Oshoala and Caldentey causing all sorts of problems for Barcelona.
The hosts were creative going forward and launched wave after wave of attacks while dominating possession, while they immediately hunted in packs to recover the ball on the occasions it was lost.
Arsenal goalkeeper Manuela Zinsberger was called into action early to push wide Hansen’s effort and Oshoala fired a low diagonal shot narrowly beyond the far post.
Marta Torrejon was next to test Zinsberger, but the Gunners managed to hold out until just past the 30-minute mark, when Zinsberger got down to push out Oshoala’s low shot at her near post, only for Caldentey to react quickest to collect the loose ball and slot in from close range.
Oshoala lashed into the side netting before dominant Barcelona did manage to double their lead just before the interval, with Oshoala driving down the right flank and into the box before cutting back for UEFA Women's Player of the Year Putellas to guide home.
Things only got worse for Arsenal immediately after half-time, with Oshoala easily racing away from Jennifer Beattie and picking up a fine through ball before coolly finishing for Barca’s third.
Vivianne Miedema’s scuffed effort was easily held by returning Barcelona goalkeeper Sandra Panos before Arsenal boss Jonas Eidevall made a triple change, replacing his front three as Tobin Heath, Nikita Parris and Caitlin Foord were all introduced at once.
Zinsberger saved from the dangerous Hansen with her legs and the confident Caldentey narrowly avoided picking out the top corner from distance.
But Arsenal began to enjoy more success after the changes, with USA legend Heath shooting wide and Parris seeing an effort cleared off the line by Mapi Leon after Barca substitute Martens had hit the side netting with a great chance just minutes after coming on.
Arsenal did reduce the deficit and provided a glimmer of hope of a late comeback when Heath’s excellent free-kick from the right bounced in off Norwegian midfielder Frida Maanum.
However, Martens would not be denied as she went close again before then finding the back of the net, sent clear in behind England defender Leah Williamson before nonchalantly lifting the ball over a committed Zinsberger.
Barcelona pressed hard to add even more gloss to a one-sided scoreline and Zinsberger made a superb point-blank stop to deny Irene Paredes and Bruna Vilamala then headed narrowly wide.
Jordan Nobbs conceded a stoppage-time penalty with a reckless sliding challenge on Putellas, who could not make it five from the spot as Zinsberger made a fine save.