Caroline Graham Hansen secured four-time champions Barça, who have reached the final six seasons running, a point after Frida Maanum fired visitors Arsenal into a surprise lead at Camp Nou.
The Gunners beat Barcelona in the 2025 final in Lisbon in the teams' last meeting and, despite Renee Slegers's team's domestic struggles, dug deep to deliver on the big stage again.
The draw leaves Barça, second, level on 10 points with leaders Lyon after four matches, while the Londoners are fourth, level on eight points with third-place Bayern Munich and Chelsea.
"Arsenal did a good job, they were well organised and tried to play football. It was a tough game, so well done to them," Graham Hansen told Disney+.
"I think we had enough chances to win the game, but that's football...
"We were shooting on target but they were there, blocking shots and doing a good job, so credit to them. We know we can do better."
Arsenal goalscorer Maanum said the point was a good result to take home from Catalonia.
"I think it was a good performance from us defensively," she told Disney+.
"We ran a lot, we disrupted their attacking game and we've come away with a point, which, against Barcelona, is quite good."
Two-time winners Arsenal had a golden opportunity in the opening stages when Caitlin Foord broke into the box but Irene Paredes blocked brilliantly.
The rebound fell to Alessia Russo, who headed against the post from point-blank range, but appeared to be offside.
Barcelona barrage
Barcelona took control after that, with Graham Hansen and Sydney Schertenleib forcing Arsenal's Misa Rodriguez into two saves at her near post.
The visitors, who are languishing in sixth in the English top flight, rode out the barrage and nosed ahead through Maanum after 22 minutes.
Barcelona goalkeeper Cata Coll saved well from Foord but Norwegian midfielder Maanum reacted quickest to latch on to the rebound and slot home.
Graham Hansen ran Arsenal left-back Taylor Hinds ragged but Barça could not break through before the interval.
Claudia Pina fired narrowly wide after a burst inside from the left and Paredes looped a header over the crossbar.
Graham Hansen's header clipped the post just before the break as Pere Romeu's Barça went in frustrated, but the Norwegian winger pulled them level before the hour mark.
Esmee Brugts found Graham Hansen in the box and she cut inside Steph Catley and whipped a strike into the top left corner.
Russo might have put Arsenal back in front but hammered over when well placed after being teed up by substitute Olivia Smith.
Three-time Ballon d'Or winner Aitana Bonmati came off the bench for Barça in the second half but could not help them find a way through.
Arsenal resisted Barcelona pressure in the final stages without many scares to end the hosts' 100 percent start to the competition.