The swearing-in ceremony was held on Wednesday in Lokoja, the state capital.
Justice Oluseyi was sworn in at 10:35 am after taking his Oath of Office.
This comes five days after Governor Bello approved Olasuyi’s appointment in an acting capacity.
The position became vacant following the demise of Justice Nasir Ajanah on June 29.
Among those that attended the ceremony are Governor Yahaya Bello, the state Deputy Governor, Edward Onaja; Speaker of the House of Assembly, Matthew Kolawole and other top government officials.
Meanwhile, Governor Bello has approved the appointment of Bayo Olowosegun as the acting President of the state’s Customary Court of Appeal.
Mr Olowosegun’s appointment also followed the demise of the former occupant of the office, Shaibu Atadoga, who died on June 22.