[5][6] He was a Director in the South Asian Association for Regional Cooperation (SAARC) Secretariat.
[10] Hamidullah served as director of the South Asian Association for Regional Cooperation Secretariat in Kathmandu from 1 February 2008 to 4 July 2011.
[1] In October 2016, Hamidullah was appointed High Commissioner of Bangladesh to Sri Lanka replacing Tarik Ahsan.
[15] He organized an event to mark International Mother Language Day in 2024 on the campus of Leiden University.
[17] In June 2024, Tareque Muhammad, the Bangladeshi high commissioner to Kenya, was appointed Ambassador of Bangladesh to the Netherlands to replace Hamidullah.