Atletico's 1-1 home draw against Malaga last week forced the title race to a thrilling conclusion at Camp Nou on Saturday, with Diego Simeone's side set to be crowned champions with a win or a draw - but Barcelona still able to defend their crown with victory.
Injuries to Diego Costa (hamstring) and Arda Turan (pelvis) inside the first 25 minutes harmed Atletico's hopes and Alexis Sanchez's stunning 34th-minute goal gave Barcelona all the momentum.
But sloppy marking from a corner would ultimately cost Barcelona, who allowed Diego Godin to steal in unmarked and head in the all-important equaliser four minutes into the second half.
Lionel Messi had a goal ruled out for offside as the hosts sought a response, but they were ultimately denied by the visitors' typically stubborn defence.
The title is Atletico's 10th in the Spanish top flight and ensures they finish the season unbeaten in all six matches they have played against Barcelona.
And although Costa and Turan's injuries will reduce their chances of winning next week's UEFA Champions League final against bitter rivals Real Madrid, Atletico will first be celebrating the end to their 18-year Liga drought.
Simeone's men led the league by as much as six points in April but stuttered late, only to produce when it counted in Barcelona, who may have played their last match for under-pressure coach Gerardo Martino.
Passed fit to play despite pre-match doubts, Costa started alongside ex-Barcelona forward David Villa while the hosts - who surprisingly left out Xavi - recalled Gerard Pique after he recovered from a hip injury sustained against the same opponents last month.
Any suggestions that Atletico would play for a draw were quashed in the early stages, as Miranda nodded a free-kick wide before Juanfran's dangerous ball into the penalty area had to be cleared by Pique.
But disaster struck for Atletico in the 14th minute as Costa pulled up clutching his hamstring and was forced off.
The striker, scorer of 36 goals in 51 appearances this season, could not control his emotions, breaking down in tears on the bench, and he would be joined by Turan nine minutes later when he failed to recover from a pelvic injury sustained in a collision with Cesc Fabregas.
Atletico's double-blow gave Barcelona a boost, and after a cagey start, they begun to create chances as Alexis and Pedro failed to convert headers after excellent crosses from Dani Alves on the right.
Pedro's failure to hit the target from a free header was particularly disappointing, but Alexis sent the partisan crowd wild in the 34th minute with his outstanding finish from just inside the area.
Messi chested down a lobbed Fabregas ball and Alexis pounced, thrashing a half-volley past Atletico goalkeeper Thibaut Courtois and into the top-right corner from an incredibly difficult angle.
Tempers frayed before half-time, with four players booked in the 10 minutes preceding the break and Atletico came out breathing fire once play resumed.
Villa was the first to go close, firing a left-foot volley into the post after beating Barcelona goalkeeper Jose Pinto with a quick shot on the turn.
The forward was then played in, but under pressure from Alves, could not get a shot off before the onrushing Pinto cleared.
Atletico did get their goal four minutes into the second half though, as the unmarked Godin made the most of Barca's flat-footed defence to score a towering header from Gabi's corner.
Neymar made his first appearance in more than a month from the bench as Martino chased the game and, in the 63rd minute, Barcelona thought they had taken the lead, only for Messi's instinctive volley - which flew into the roof of the net from close range - to be adjudged offside.
Alves had a fierce strike tipped over in the latter stages, but despite their late pressure, Atletico clung on and were applauded for their efforts by the Camp Nou faithful at full-time amid wild celebrations from the small contingent of away supporters.
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