The review of specimens from Iran belonging to the Portulaca oleracea L. aggregate resulted in the recognition of six microspecies: P. cypria Danin, P. granulatostellulata (Poelln.) Ricceri & Arrigoni, P. nitida (Danin & H.G.Baker) Ricceri & Arrigoni, P. rausii Danin, P. socotrana Domina & Raimondo, and P. trituberculata Danin, Domina & Raimondo, all reported for the first time for the flora of Iran. The identification was based on the microscopic study of seeds. It is noted that P. oleracea is not confirmed for Iran. Distribution data and an identification key for Portulaca microspecies in Iran are presented.