Evan Mawarire was arrested at Harare International Airport on Wednesday, accused of subverting a constitutionally-elected government.
His lawyer, Harrison Nkomo, said the allegations come partly from his role in organising protests against Mr Mugabe in New York during the UN general assembly in September last year.
The Baptist cleric is also accused of using social media to incite “violent demonstrations”.
It follows a Facebook video posted in April last year, in which Mr Mawarire wrapped himself in a Zimbabwean flag and complained about the state of the nation – sparking the #ThisFlag protest movement against the country’s leadership.
He left Zimbabwe soon after, taking his family to America.
It is not clear why he chose to return home.
Muleya Mwananyanda, Amnesty International’s deputy regional director for southern Africa, has described the allegations against Mr Mawarire as “absolutely ridiculous and a total sham”, saying he was being punished “for speaking out about the declining human rights situation”.
Mr Mugabe has said Mr Mawarire and other protesters should leave Zimbabwe if they are unhappy with the country’s situation.