Atleti goalkeeper Juan Musso was forced into action inside 33 seconds, diving full-length to his right to keep out Lamine Yamal’s curling effort.
In the fourth minute, a defensive mix-up from the hosts saw Ferran Torres play in an unmarked Lamine, and he stroked Barca ahead.
The tension was palpable around the arena, as Barca began to dominate possession, and after another mistake - this time from Kok3 – Torres smashed home a magnificent left-foot effort into the top corner to level the tie on aggregate.
Barely a minute later, Fermin Lopez should’ve made it three, but headed straight at Musso, before the keeper’s stray boot cut Fermin’s face, leading to a long stoppage.
Not long after the game restarted, Atleti’s Ademola Lookman scored a simple tap-in, meaning Barca became the first team in UCL history to have not kept a clean sheet in 15 consecutive games.
A similar pattern at the start of the second half saw Atleti sitting much deeper in a back-five system, looking to break at pace with balls over the top.
More Barca pressure saw Ferran volley home instinctively, before it was overruled by VAR for offside, sparking delirium in the stands.
The visitors continued on the front foot, with Lamine at the heart of everything, but the longer the game went on, the more likely Atleti were to progress.
Joan Garcia’s point-blank save from Robin Le Normand kept Barca in the tie, before Eric Garcia was sent off for a professional foul with just over 10’ to play.
The final moments of the game saw an all-out attack from the visitors, but it just wasn’t enough to force extra time.
The result sees Atletico Madrid continue their remarkable record of never having failed to progress in the UCL knockout stages after winning the first leg away from home (22 attempts).
Meanwhile, Barcelona have now lost seven of their last 10 UCL quarter-final ties, and are left to concentrate on wrapping up the LaLiga title.