The result saw Barcelona coach Gerardo Martino pay for his club's failures at home and abroad with his job as he immediately stepped down from his role minutes after the full-time whistle had sounded.
Martino had been widely expected to leave, win or lose in last night's crunch clash and Barcelona confirmed the news at his post-match press conference.
"Martino has announced that, by mutual agreement with the club, he ceases to be the coach of FC Barcelona," the club said on their Twitter account.
It was the culmination of a dramatic finale to La Liga after Atletico's Diego Godin's headed equaliser early in the second half was enough to deny Barcelona in a tense decider.
The hosts had taken the lead with a stunning strike from Alexis Sanchez, but it was a rare sight of goal for the hosts, with Lionel Messi cutting a frustrated figure and Atletico's defence standing firm.
Martino sprung a surprise in his team selection with Barcelona's most decorated player Xavi Hernandez left out as Cesc Fabregas and Sergio Busquets started alongside Andres Iniesta, while Pedro Rodriguez was preferred to record buy Neymar.
Atletico started with former Barca man David Villa alongside Diego Costa, with Raul Garcia among the substitutes.
Tension was high from the start with Atleti making a bright start and Gerard Pique earning an early yellow card for fouling Koke. Barcelona had most of the ball, but could not find a way to test Thibaut Courtois while Atletico's breaks looked dangerous as Jose Pinto was hesitant in goal.
Atletico's hopes suffered a huge blow in the 14th minute when Costa pulled up with a recurrence of his hamstring injury, leaving the pitch in tears with his chances of playing in Saturday's Champions League final in the balance.
It got even worse moments later when Arda Turan followed him off after taking a blow from Fabregas, and the wind was in Barcelona's sails.
Alexis' wonder strike put them ahead in the 34th minute, with the Chilean rifling a shot into the roof of the net from an acute angle.
Atletico were in danger of losing their cool in the moments that followed as Godin and Tiago collected yellow cards, but they hung on until half-time.
Manager Diego Simeone looked to have worked some kind of magic in the dressing room and his side started the second half on fire, with Villa striking the post 45 seconds after the restart before Godin headed them level in the 48th minute, rising highest to power a header into the bottom corner of the goal.
Injuries then began to strike at Barcelona, with Busquets forced off. Alex Song was the man to replace him as Xavi remained on his seat, and a second substitution soon after saw Neymar replace the ineffective Pedro. Messi raised Catalan hopes when he hammered the ball into the roof of the net in the 64th minute, but the little Argentine was clearly offside.
Xavi then came on to replace Fabregas with 12 minutes to go as Barcelona went into all-out attack mode, and Courtois palmed over a powerful Alexis strike as the game moved into the final 10 minutes.
The breathless action continued as Pique demanded a penalty in vain after being eased over by Godin. Tension levels rose, but Barca could not find a way past a dogged Atletico defence. Pinto raced up for a stoppage-time corner, but Atletico pumped the ball clear and seconds later their party began. Barcelona's fans stuck around to applaud, a fitting end to a pulsating title race.
lChampions League final preview - pages 10&11