Okeke defected to the All Progressives Congress (APC) at the presidential villa, Abuja, on Wednesday.
He was presented to President Muhammadu Buhari by Mai Mala Buni, Yobe state governor, and Hope Uzodinma, the Imo state governor.
Okeke’s defection comes less than a month to the November 6 governorship election in Anambra.
APGA is the ruling party in Anambra state.
Willie Obiano, Anambra governor, had recently alleged that members of APGA in the state house of assembly were induced to join APC.
The governor said some of the lawmakers were given N100 million each to defect.
“Any time, any day, there’s no other party in Anambra. Only APGA, there’s no APC,” he had said.
“Those people that went to APC, they went to collect money because they saw the additional money, N100 million each, they are still APGA, they are giving us information on what is happening in APC.”
Obiano had also accused the APC and Abubakar Malami, attorney-general of the federation, of trying to destabilise Anambra.
He made the comment after Malami had said the federal government may declare a state of emergency in Anambra to ensure the governorship election takes place.
Reacting, Obiano said: “Anambra is doing well, and don’t forget that Malami is on the national campaign committee for the APC candidate. So, if that’s their strategy, then they failed already. Come to the ballot box, APGA will win and win hands down.
“They are trying to see how they can destabilise us. No! APC has no room in Anambra. There’s no party called APC in Anambra. Anambra is APGA.
“We’ll have enough security to back the people and Professor Chukwuma Soludo will be the next governor of Anambra state.”
Chukwuma Soludo, former governor of the Central Bank of Nigeria (CBN), is the flagbearer of APGA in the governorship.