This was Barca's fourth game of preseason and the first they have failed to win. They're still without Lionel Messi, who's not yet signed his new deal with the Catalan club and remains a free agent.
Barca were also missing several other players due to injuries, the Olympic Games and players returning late from international tournaments this summer.
It was the home side who roared out of the blocks in a front of a ferocious crowd, though, and they should have been 2-0 up before Sucic's 43rd-minute opener.
At the other end, Memphis curled wide for Barca and Griezmann hit the roof of the net but Nico Mantl was never really troubled.
Salzburg finally opened the scoring on the stroke of half-time when Sucic's long-range effort took a touch off De Jong to deceive Neto.
Multiple substitutions disrupted the second half, but Salzburg remained on top and there was still time for Okafor to miss another opening, firing straight at Neto when well placed, before he was finally replaced.
The game opened up late on, with Alejandro Balde and Memphis both testing substitute goalkeeper Philipp Kohn from distance before Braithwaite's leveller.
Salzburg pushed hard in the final five minutes to restore their lead. Some last-ditch defending from Dest kept Benajamin Sesko out on the line but the home side kept going.
Adamu shook the post but Aaronson, who scored seven goals in his debut season in Salzburg last term, was quickest to react to the loose ball.