The main benchmark of Tehran Stock Exchange, TEDPIX, pared all gains in the early hours of trade to shed 751.07 points or 0.06% ending trade at 1,362,344.
Big winners were auto, banks and telecom stocks while prices in almost all other share categories declined.
Retail trade rose 25% to reach 28.26 trillion rials ($100 million), accounting for 59% of total Saturday trade.
As the session ended, 156 tickers were in positive territory and prices in 327 tickers declined, accounting for 66% of the total.
About 6.2 billion shares valued at 28.2 trillion rials ($100m) changed hands at TSE for the day.
Trading at TSE and junior exchange Iran Fara Bourse starts on Saturday and ends Wednesday.
Mahram Manufacturing Group Company was the biggest winner as its shares went up 4.8% to 9,600 rials per share.
Amin Investment Bank incurred the biggest loss among all TSE-listed companies and went down 4.95% to 10,380 rials per share.
Persian Gulf Petrochemical Industries Company contributed the most to the benchmark's fall, followed by Mobarakeh Steel Company, Nouri Petrochemical Company and Shazand Petrochemical Company.
Iran Khodro Company gave the biggest boost to the benchmark index followed by Mellat Bank, Bank Saderat Iran and Saipa Automaker Company.
IFB Loses 0.16%
Iran Fara Bourse main index, IFX, lost 28.83 points or 0.16% to close Saturday trade at 18,374. About 164,975 shares and securities valued at 26.53 trillion rials ($94.7m) were traded at the junior exchange for the day.
Rail Pardaz Noafarin Company had the highest number of traded shares as 26.68 million of its shares worth 108.15 billion rials ($386,271) were traded.
Minoo Industrial Group Company, Zagros Petrochemical Company, Hormozgan Steel Company and Tabas Parvardeh Coal Company had the most negative impact on IFX.
Melal Credit Institution gave the biggest boost to IFX, followed by Arya Sasol Polymer Company, Negin Software Systems Development Company and Alborz Distribution Company.