Beikzadeh sustained a calf injury in a 0-0 draw with Montenegro on Monday, and the Iran Football Federation is awaiting news of a medical report.
However, even if Beikzadeh is cleared to play in Brazil, his replacement Mohammad Reza Khanzadeh is expected to travel with the squad.
Forward Mohammad Reza Khalatbari is a surprise omission, having been a regular during Iran's qualifying campaign.
There is also no place for winger Sardar Azmoun, a reported transfer target for Arsenal, while goalkeeper Sosha Makani and striker Mehdi Sharifi also miss out.
Iran begin their Group F campaign against Nigeria on June 16, while Argentina and Bosnia-Herzegovina are also in their pool.
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