As well as welcoming Boko Haram's loyalty, the speech also threatens further violence against Christian and Jewish communities according to News Week.
An audio message released in the name of ISIS leader Abu Bakr al-Baghdadi, he accepted the pledge of allegiance offered by Boko Haram’s leader Abubakar Shekau.
Speaking for his leader Abu Bakr al-Baghdadi, the man in the recording says: 'We announce to you to the good news of the expansion of the caliphate to West Africa.
'Our caliph has accepted the pledge of loyalty of our brothers of Boko Haram so we congratulate Muslims and our jihadi brothers in West Africa.'
He urged Muslims who could not join the fight in Syria to enter the conflict in Africa instead.
Nigerian President has claimed Boko Haram insurgents have already traveled to the Middle East to train with ISIS militants, according to Voice of America.
The insurgents have killed thousands in bomb attacks and violent sieges on villages in the remote north-east, and are now feared to be spilling over into neighbouring Cameroon and Chad.
Members of the UN Security Council have called on the international community to supply money, equipment, troops and intelligence to the five-nation African coalition fighting them.
Boko Haram killed an estimated 10,000 people last year and took responsibility for last April's abduction of more than 275 schoolgirls.