Established in 1917, UBN is a publicly-traded bank that offers services through its 340 branches in Nigeria. It had assets of around $6.3bn at the end of June 2014.
After completion of the transaction, Atlas Mara will own a total of 29.9% stake in UBN, which includes the shares already held by Atlas Mara through its ADC African Development division.
Atlas Mara CEO John Vitalo said: "Expanding into Nigeria has been a focal point of our strategy and achieving a significant ownership position in an institution of the size, heritage and potential of UBN represents a unique opportunity.
"We at Atlas Mara are committed to building a leading sub-Saharan African financial services group and we look forward to contributing to the transformation of UBN into a Tier 1 Nigerian bank as an integral part of this strategy."
Atlas Mara co-founder and director Bob Diamond said: "We will have a significant stake in a key Nigerian bank and we will also have established strategic market positions in three of Africa’s leading economic communities: the Southern Africa Development Community, the East Africa Community and Economic Community of West African States."
The transaction is subject to certain regulatory approvals.
