A by-election was held on 21 February 2020 for three vacant seats of the Assembly of Experts in Tehran Province, caused by death of Akbar Hashemi Rafsanjani, Nasrollah Shahabadi and Abolfazl Mirmohammadi. It was held along with the 2020 Iranian legislative election.

In contrast to the competitive 2016 election which the moderate list had won by a landslide, it was an uncontested election without presence of such candidates and resulted in victory of all three candidates supported by The Two Societies.

The number of invalid votes cast in the election and its turnout were not officially declared by the authorities. Results #CandidateElectoral listVotesNotesCCASST1Ali Momenpour 963,605 Elected2Abbas-Ali Akhtari 961,773 3Gholamreza Mesbahi-Moghadam 708,774 4Hossein-Ali Sa'di 487,605 Defeated5Gholam-Abbas Haghemi 243,8016Ali Rahmanifar 194,126 7Ali Razini 176,024 8Seyyed Sadegh Mohammadi 159,792 9Mohammad-Ali Amin 158,453 10Hamid Shahriari 122,095 11Ahmad Mousavi-Vadeghani 115,700 12Mohammad-Ali Khazayili 90,875 13Hossein Radaei 79,925 14Mohammad-Sajjad Mousavi 60,214 Blank/Invalid VotesNot DeclaredValid Votes1,924,015Total VotesNot Declared100Source: Tehran Province Governorate / Ministry of Interior / ISNA References