Sigma Huda, a UN special rapporteur on people trafficking, had her application for bail rejected by the Supreme Court.
Mrs Huda faces allegations of having wealth disproportionate to her income. She denies the charges.
She is among scores of high-profile figures in Bangladeshi public life who have been detained in a crackdown on alleged corruption in recent months.
'Immunities'
Mrs Huda had been granted bail by the high court, but the Supreme Court overturned the ruling on Wednesday.
On Thursday, she appeared before a special anti-corruption court which ordered that she be detained for the remainder of her trial, which is already under way.
In June, UN officials sought to clarify her fate when it emerged that she was being prevented from leaving the country.
A spokesman said the Bangladesh government had been asked "how, in light of the convention on privileges and immunities of the UN... such proceedings allow for keeping her from attending to her duties as special rapporteur".
Mrs Huda had been due to address the UN Human Rights Council in Geneva.
Her husband, Nazmul Huda, was communications minister in the government of Bangladesh Nationalist Party leader Khaleda Zia, which left power in October.
He is among scores of senior politicians and business leaders rounded up in the anti-corruption drive. He also denies wrongdoing.
Bangladesh's caretaker administration declared a state of emergency in January and postponed elections after months of political violence.