"I regret that a large number of people among the political elite and others have been arrested, and I ask for their release," Zahra Rahnavard said in remarks published on her husband's campaign website.
"I have not been arrested. I continue my work at the university, but at the same time, alongside others, I protest" the result of the election, which put Mousavi a distant second after victorious incumbent Mahmoud Ahmadinejad.
"Nationalism and the blood of the martyrs demand that I be on the scene, always protesting against the result of the election and defending people's rights within the framework of the law."
She said the regime should not act as if Iran were in a "state of siege."
Since the election, whose outcome is disputed by Mousavi, Tehran and other parts of the country have been the scene of often violent protests.
Hundreds of protesters have been arrested, as well as politicians and journalists.
Rahnavard, 64, a sculptor and academic, broke the mould of Iranian politics by campaigning openly alongside her husband ahead of the vote.
