His family says Mwinyi is receiving treatment for a chest illness and is under the care of doctors.
Former Tanzanian President Ali Hassan Mwinyi was hospitalised on Friday, the Zanzibar presidency announced.
A statement from his family shared by Deputy Director of Presidential Communication State House Zanzibar, Mohamed Hashim, said Mr Mwinyi, who is now 98 years old, is receiving treatment for a chest illness and is under the care of doctors.
The family asked for privacy and prayers for the former head of State.
“With advice from his doctors, the family has decided that it is good that he gets privacy while receiving treatment. The family asks the public to pray for him,” wrote the family spokesperson and son of the former leader Abdullah Mwinyi.
Mr Mwinyi was the second President of Tanzania between 1985 and 1995. His son Dr Hussein Ali Mwinyi, is the current President of Zanzibar, in the Tanzanian archipelago.