The announcement was made by Senate President Bukola Saraki.
Akpabio, a first term senator, was nominated by the South South caucus of the Peoples Democratic Party (PDP), the party which lost the majority to the All Progressives Congress (APC) in the last election.
His nomination violated the standing rules of the Senate, which reserves principal leadership positions for only ranking senators.
A Federal High Court last week rejected an application seeking to stop him from being named Minority Leader.
Two PDP senators had gone to court to challenge the move.
But the former chairman of the PDP Governors’ Forum in the last dispensation works in uncommon ways.
He beat off all obstacles on the way to receiving wide support from colleague lawmakers and his party.
Also on Tuesday, Phillip Aduda, who represents the Federal Capital Territory, was named Minority Whip, while Emmanuel Bwacha, representing Taraba State, emerged Deputy Minority Leader.