Pacquiao weathered an exciting start from the undefeated challenger in the opening two rounds to wear the American down throughout the middle portion of the contest and had Bradley seriously reeling after six.
Bradley would show great resilience and edge some of the later rounds after going back to basics and working the jab from distance, but there appeared to be no confusion amongst the live attendance or either camp as to who was the better man.
It came as a shock when the judges' scorecards all read 115 to 113 - with two of the three in favour of the new champion.
Bradley's performance would have no doubt raised his stock even in defeat, but the unexpected nod from the men in charge of the final outcome is destined to catapault 'Desert Storm' to even greater heights.
His first order of business could well be an immediate rematch: Pacquiao has a clause in the fight contract, and both fighters expressed a willingness to settle things once and for all in a return bout in their post-fight interviews.
"I’ve got to give Manny a rematch," Bradley admitted.
"I know the fans weren’t happy with the result and I’ve got to give Manny his chance to win the title back.
"I caught my second wind after the sixth round. I kept sticking and moving with my jab and caught him with clean shots.
"Manny is very fast and very hard but I have strong legs and my will to win prevailed.
"My corner told me that if I can win the last round, we will win the fight and that’s what we did."
Pacquiao drew some pre-fight controversy of his own by having the bell-time delayed courtesy of a previous agreement which would ensure he could watch the NBA Eastern Conference game seven between Boston Celtics and Miami Heat.
But the Filipino insisted the situation did not affect him, saying: "I was very warmed up as I headed into the ring and it was a good fight.
"I’m disappointed but he moves very well and he’s undefeated for a reason. I thought that I won the fight, though.
"I’ve been watching his fights and he’s an aggressive boxer, but he didn’t really hurt me. Most of his shots hit my arms. I don’t know what happened.
"I am willing to have a rematch, no problem. And if he’s ready to do it, credit to him."
YAHOO!-EUROSPORT ROUND BY ROUND:
Round one: It is Bradley who edges the early exchanges, landing more jabs and catching the champ with a couple of decent counter-strikes. But Pacquiao finds his groove in the closing stages and lands well in response. Even opening round. Yahoo!-Eurosport scorecard: 10-10.
Round two: Bradley starts the second round strong, catching Pacquiao on three occasions in the first half of the round before flustering him with a lightning-fast combination soon after. The champion takes the shots in his stride, however, and retains good positioning throughout. Nonetheless, a pair of connections with the Filipino’s chin hand the round to the challenger. Scorecard: 20-19 Bradley.
Round three: Pacquiao works the angles for leverage and lands a series of solid lefts as a result. Bradley responds with some light one-twos only to receive a vicious left and further combinations in a scintillating climax to the best round so far. Scorecard: 29-29.
Round four: The champion continues to exploit his challenger with more combos and a pair of pinpoint body blows which the American, to his credit, is able to weather and avoid a stoppage. Nonetheless, a clear 10-8 for Pacquiao. Scorecard: 39-37 Pacquiao.
Round five: Calmer round after a blistering display in three and four, but another left to the body weakens a flagging Bradley further in the closing 30 seconds. He finishes the fifth swinging, but it's another one for Pacquiao. Scorecard: 49-46 Pacquiao.
Round six: Bradley keeping Pacquiao at bay early on with the jab, but with little behind it especially compared to his decent throws in the first pair of rounds. Pacquiao again turns up the heat in the closing stages, cornering the challenger before landing a slick uppercut. Scorecard: 59-55 Pacquiao.
Round seven: Straight left by Manny halfway through wakes up an otherwise pedestrian round.Pacquiao shakes off a couple of decent head shots from the American and responds with a succession of his own, but receives two warnings for holding Bradley’s head down. Scorecard: 69-64 Pacquiao.
Round eight: Pause as the two clash heads, and Pacquiao gets away with another push down. It's an edge for Bradley despite a late one-two in the final ten seconds from the champ. Scorecard: 78-74.
Round nine: Bradley gets closer to the champion in hopes of smothering his game, and connects with an uppercut of his own followed by a hook in the final 30 only to leave himself open to Pacquiao's own combos.Pacquiao shades the ninth. Scorecard: 88-83.
Round 10: Quiet tenth, plenty more distance between the two but it's Bradley who lands more and finally shows command of the space inside the ropes. Scorecard: 97-93 Pacquiao.
Round 11: Pacquiao may feel as if he's done enough: he is happy to play along with Bradley's distance game which is drawing scant pockets of boos from the action-hungry live crowd. He finishes strong in the final 40 seconds, however, with enough clean shots to take the round. Scorecard: 107-102 Pacquiao.
Round 12: Bradley finishes with his head held high, landing a sporadic series of straight shots, but a belting left from Pacquiao in the final seconds puts an exclamation point on a cerebral and superior performance. Final Yahoo!-Eurosport scorecard: 117-112 Pacquiao.