The BNP leader and his wife Rahat Ara Begum caught a Biman Bangladesh Airlines flight on Monday evening.
He will receive treatment at the National University Hospital there.
Mirza Fakhrul has problems in his internal carotid artery.
The Supreme Court in 2015 granted him bail for treatment abroad for the same problems when he was in jail.
He has travelled to New York, Singapore and Thailand several times for treatment since then.
He went to Singapore for medical check-up for the last time in July last year.
