The National Endowment for the Humanities, an independent federal agency and the foremost sponsor of educational and research projects in the field of humanities, recognized the need for and significance of the Encyclopædia Iranica, which it classified and supported as a “major project” from 1979 to 2016, an impressive exception both in terms of the duration of sponsorship and the amount of support accorded to research-tool projects.

The American Council of Learned Societies endorsed the Encyclopædia Iranica. Professor Stanley N. Katz, former ACLS President, wrote to the Editor: “It is an honor for the ACLS to have even this remote connection to such a distinguished academic undertaking, and I congratulate you on this success and wish you the best of luck in the continued excellence of the Encyclopaedia.”

In June 1997, following the sponsorship of The American Council of Learned Societies, the Union Academique Internationale voted unanimously to extend its patronage to the Encyclopædia Iranica project.

In 1990, the Getty Grant Program, well-known for its sponsorship of art history and archeology studies, also recognized the particular contribution of Encyclopædia Iranica in these fields by allocating a substantial grant for a 3-year period.

Many foundations, organizations, and individuals with an interest in Iranian culture have supported Encyclopædia Iranica over the years. Khosrow Eghbal, a former chairman of the Encyclopædia Iranica Foundation, bequeathed the largest gift for the Encyclopædia. Mahmoud Khayami, Abtin Sassanfar, Khosrow and Ghazaleh Semnani, Akbar Ghahary, Sadigheh Rastegar, Iran Heritage Foundation, Soudavar Memorial Foundation and Persian Heritage Foundation have made substantial contributions over the years to support the Encyclopaedia Iranica.