Darya Safai, who sat in a front-row courtside seat and was briefly in tears during the ordeal, said that Olympic officials told her today they would ask her to leave if she didn't put her sign away.
The International Olympic Committee bans political statements at the games.
Safai plans to try to bring her cause to Maracanazinho arena again. She wore a headband with the colors of Iran's flag and also face paint of the flag on each cheek.
Based in Belgium, Safai is the founder and director of "Let Iranian Women Enter Their Stadiums!" and an activist against gender discrimination.
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Women have generally been banned or heavily restricted from attending all-male sports events in Iran.
Iran's volleyball team, in its first Olympics, swept Egypt in the match 3-0 for its second victory in Rio.
In 2012, the longtime ban on women from soccer matches in Iran was extended to volleyball.
USA Volleyball chairwoman Lori Okimura has been outspoken on the issue and she even brought her own "Let Iranian Women Enter Their Stadiums" T-shirt along to Brazil and checked in with Safai today to make sure she was OK.
"This is not a political statement. This is not a political issue," Okimura said. "This, to me, is not about politics, it's about gender.
Volleyball has always been about equality, why now are we not sending that same consistent message?"
Women in Iran saw her efforts on TV and appreciated the solidarity, taking to social media in support of Safai.
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