A goal from Ousmane Dembele in the first-half and a late Lionel Messi penalty were enough to see Barca to all three points as they bounced back from a traumatic week with a win.
Defeat in Saturday's Clasico was followed by the resignation of club president Josep Maria Bartomeu on Tuesday.
Their task in Turin was made easier with Ronaldo missing after a third positive test for coronavirus ruled him out of another meeting with rival Messi.
And Barcelona's official Twitter account couldn't help but make a joke at his expense.
"We are glad you were able to see the real goat (emoji) on your pitch @juventusfcen!," they posted after the game.
"You probably looked it up in the wrong dictionary. We'll bring you the right one at Camp Nou," Juve replied.
Barcelona now have the sole lead of Group G, three points above Juventus. Dynamo Kyiv and Ferencvaros have one point each after drawing 2-2 on Wednesday.
"I believe it was the most complete match since I arrived," coach Ronald Koeman said. "I think the team showed a lot of personality in midfield, it was our best game.
"We had a great game against a great team. I think we showed our best soccer. We created a lot of scoring opportunities. I'm very happy with the play, I'm very happy with the character of the team, a great victory.
"Today the team showed that it wasn't affected by yesterday's news. I can't say it surprised me. President Bartomeu took this decision for the good of the club."
— FC Barcelona (@FCBarcelona) October 28, 2020
The scoreline could have been worse for Juventus if the visitors had been more clinical with their chances.
Juventus threatened little but, as well as Ronaldo, they were also missing key players Giorgio Chiellini, Matthijs de Ligt and Alex Sandro.
"We have young players who still don't have these type of matches in their heads so they suffer a bit more," boss Andrea Pirlo said.
"They all had a good game but then they were a bit tired because we also didn't have players to change, and then it's normal to suffer against Barcelona.
"We have to wait to get players back, because we have some important ones out."
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