American Bradley won a split decision at the MGM Grand in Las Vegas on June 10 that prompted disbelief from the sporting world and had many calling the outcome corrupt.
The WBO met with five international judges to evaluate video of the match and they unanimously scored the fight in favour of Pacquiao, though they do not have power to overturn the initial ruling and the result will still stand.
Although the Nevada State Athletic Commission does have the power to formally overturn the decision, it has refused to launch an internal inquiry into the result.
The quintet of officials scored the fight 115-111, 116-112, 117-111 117-111 and 118-110 retrospectively - all in favour of the Filipino.
The Yahoo!-Eurosport scorecard had the eight-division world champion as the winner by 117-112, with the final round an even score.
Pacquiao has indicated that he would prefer a rematch over Bradley forfeiting the belt, according to Bob Arum, the promoter for both fighters.
He told ESPN: “My supporters shouldn’t worry. We’re going to get that title.”