Adeleke, who contested on the platform of the Accord Party, was declared the winner on Sunday morning after the collation of results at Osogbo, the state capital.
Declaring the result, the Independent National Electoral Commission (INEC) Returning Officer for the election, Joshua Ogunwole, said Adeleke polled 511,067 votes to emerge victorious.
Oyebamiji finished second with 444,815 votes, while the African Democratic Congress (ADC) candidate, Najeem Salaam, came third with 17,180 votes.
The result gave Adeleke a winning margin of 66,252 votes over his APC challenger.
According to the declaration, Adeleke secured victory in 19 local government areas, while Oyebamiji won in 11 LGAs.
The election was conducted amid heightened political tension following reports of violence and attacks in some parts of the state in the days leading to the poll.
Despite the concerns, voting commenced early in many areas, with substantial voter turnout recorded at several polling units.
The exercise, however, was not without challenges, as glitches involving the Bimodal Voter Accreditation System (BVAS) reportedly caused delays at some polling units.
There were also reports of alleged vote-buying, voter intimidation and harassment of journalists in some locations, although election-day violence was described as relatively limited compared with concerns raised before the poll.
With the declaration of the result, Adeleke secures another four-year mandate to govern Osun State, while Oyebamiji and the APC now face the outcome of a closely fought electoral contest.
The election had attracted significant attention because of the fierce contest between the ruling political forces in the state and the APC, with both major candidates expressing confidence ahead of the poll.
