One of the six arrested posted a message on Instagram, saying she had been released.
In the photo post, fashion photographer Reihane Taravati said she was glad to be released.
Police said the arrests had been made over a "vulgar clip" that had "hurt public chastity".
The YouTube video showed three men and three unveiled women dancing on the streets and rooftops of Tehran to the soundtrack of Pharrell Williams' song, 'Happy'.
On Tuesday, state-run TV broadcast what it reported as a video confession from the dancers.
In the edited video, the dancers were filmed from behind saying they were tricked into making the video.
"They told me they are making a feature film and they had a permit for it," one of the six said in the video.
Williams himself took to Facebook, posting a message condemning the arrests as unjust.
"It is beyond sad that these kids were arrested for trying to spread happiness," the singer wrote on Facebook.
CNN reported that the director of the video had not been released, citing the International Campaign for Human Rights in Iran.
The 'Happy in Tehran' video clocked up more than 165,000 views on YouTube before police attention forced the video to be made private. However, the video has sprung up on other YouTube accounts.
Iranians at home and abroad expressed anger at the arrests, with many using the hastag #FreeHappyIranians to express support for the six dancers.
