After 12 rounds at the Scottish Exhibition Centre, the three ringside judges could not split them, with one awarding 115-112 for the Scot, another 115-113 for the Mexican and the third scored it 114-114.
Burns came out to a rapturous ovation from the Glasgow crowd, and it did not take him long to seize the initiative. Looking far more accomplished than in his last outing against Jose Gonzalez, he rained in a few thudding right hands to take an early lead on the scorecards.
The Scot - making the fourth defence of his strap - had already damaged the left eye of the Mexican, who started to come on strong midway through the second round.
The fight was level after the fourth round, in which Beltran nearly sent Burns to the canvas. It was a thunderous left hook that caught Burns flush on the chin, sending him backpedaling. However, he managed to retain his balance to save from dropping a 10-8 round.
The challenger was unrelenting in his pressure, which forced Burns to initiate a series of clinches as he struggled for an answer.
Burns looked like he had weathered the storm in the seventh round. Another good was to follow, with Beltran appearing to take a breather.
Just as Burns looked like he had regained his composure, a massive left hook out of absolutely nowhere sent him crashing to the mat early in the ninth. He took a knee as the referee counted to eight and had to survive virtually the full three minutes as Beltran chased him around the ring.
After the ninth round, Burns told his corner that he was suffering with a jaw problem. He was reluctant to engage Beltran on the inside, but the pressure tactics of the Mexican allowed him no respite.
A spirited 12th round did not look to be enough to turn the tide for Burns, who appeared to concede defeat as soon as the final bell tolled - although his reaction was as much down to the excruciating pain of a dislocated jaw.
After announcer Michael Buffer read out the scores, there was a stunned silence around the arena, as no-one could quite believe how Beltran did not win the fight.