The Iranian national team's official Twitter accounted posted a photo of a female football fan in the stands of the Azadi Stadium in Tehran, holding a flag as she watched her team play Spain via a broadcast. Iran lost a closely-fought game 1-0.
Pictures from photo agencies show Iranian football fans -- both men and women -- arriving at the Azadi Stadium dressed in their national team's colors.
Iranian women can be seen blowing horns, while others posed for a selfie to record the moment.
Previously, Iran has banned women from watching men's sporting events and breaking the rules could result in arrest, fines or even imprisonment.
According to the Twitter account of Tara Sepehri Far
-- quoting Iranian news sources -- at one point the screening had been canceled.
"But the doors are now open and screening will happen. Just unnecessary drama, anger and inconvenience for the fans who had bought tickets," tweeted Sepehri Far, who works as a Human Rights Watch (HRW) researcher.
HRW has criticized the ban on women, which also runs counter to the FIFA statues, which prohibit gender discrimination. Article Four says discrimination of any kind is "punishable by suspension or expulsion."
However, it remains to be seen whether Wednesday's event signals a permanent shift in allowing Iranian women to watch men's sporting events.
After the game Sergio Ramos, captain of the winning Spain team, tweeted: "They are the ones who won tonight. Hopefully the first of many."
In a statement sent to CNN when Iran played their first World Cup game against Morocco on Saturday, FIFA said President Gianni Infantino had been reassured by Iranian President Hassan Rouhani during a March visit that the ban on women would eventually be lifted, though no time frame was provided.
The Center for Human Rights in Iran also posted photos of women inside the Azadi Stadium, saying: "All they are asking for is to be treated as EQUALS." The Center is not in Iran, but was posting other people's photos.
Spain took a big step towards reaching the knockout stages with their hard-fought win over Iran on Wednesday.
After a stale first 45 minutes, which Spain dominated but rarely threatened, Diego Costa broke the deadlock less than 10 minutes into the second half, albeit with a huge slice of good fortune.
Iran thought they had found the equalizer soon after, but another feather in the cap for the Video Assistant Referee saw the goal correctly ruled out for offside.
Spain's struggles against Iran continued the trend of the big nations struggling in Russia.
Brazil, Argentina and Germany all failed to win their opening games, while France, England and Portugal -- in their second game -- all labored to secure three points against lower-ranked opposition.
Of the top eight favorites to win the World Cup, only Belgium recorded a convincing result, comfortably beating Panama 3-0.
As the first half wore on, Spain were just beginning to show signs of frustration; Isco first contriving to get in David Silva's way in the box, before Jordi Alba slammed his fist into his palm after Sergio Busquets' over hit pass.
The opening half an hour felt more like a training exercise -- 11 attackers against 11 defenders -- and Spain, for the first time, were starting to find holes in the resolute Iranian defense.