Ireland's former President Mary Robinson will lead a panel investigating the leader of the African Development Bank (AfDB) Akinwumi Adesina.
The panel will be reviewing the report of the AfDB Ethics Committee, which cleared Mr Adesina of corruption accusations in early May.
However, pressure for an independent investigation has persisted, with the US rejecting the initial inquiry that cleared him.
A 15-page report earlier this year claimed that under his watch the bank had been marred by poor governance, impunity and favouritism. Mr Adesina has denied all the allegations.
Ms Robinson will lead the probe, alongside Gambia's Chief Justice Hassan Jallow and the World Bank's integrity vice-president Leonard McCarthy, the bank's board of governors said in a statement on Wednesday.
The inquiry is due to deliver its findings in two to four weeks.
The AfDB plays an important if largely behind-the-scenes role in African economies, financing projects in agriculture, health, energy, education, transport and other development sectors.