As a member of the persecuted Baháʼí Faith, Amanat fled the country during the 1979 Iranian Revolution.

[7] He is the brother of Abbas Amanat, Professor of History & International Studies at Yale University.

Since moving to Canada in 1980, Hossein Amanat designed the three administrative buildings on the Baháʼí Arc in Haifa, Israel, the Baháʼí House of Worship in Samoa,[2][8][9][10] the Jiang'an Library for the Sichuan University, the media library for the Beijing Broadcasting Institute.

He designed religious and cultural centers for the Baháʼí Faith near Dallas, Seattle and Washington, D.C., several multifamily condominiums in Santa Monica, and mixed-use high-rise buildings in San Diego and Burnaby.

On 7 May 2019 the Universal House of Justice announced Amanat as the architect of the future Shrine of ʻAbdu'l-Bahá.