Vatican spokesman Greg Burke said the Holy See was "profoundly saddened" by the situation of Peter Shao Zhumin, who he said has been missing for some time from his diocese in Wenzhou in southeastern China.
"The diocesan Catholic community and his relatives have no news or reasons for his removal, nor do they know where he is being held," Burke said.
According to the specialist religious website Asianews.it, Shao Zhumin has been in detention since May 18.
His friends fear the authorities are trying to force him to switch from the underground church recognised by the Vatican to the state-run Chinese Patriotic Catholic Association (CPCA).
Burke said the cleric's treatment, and similar episodes, would not help the efforts to reach an understanding with the Chinese authorities on the status of the Church in the communist state.
"The Holy See hopes that Bishop Peter Shao Zhumin may return as soon as possible to his diocese and that he be allowed to carry out his ministry in peace," Burke said.
Such public friction between the Vatican and China has been rare of late against the backdrop of discussions aimed at improving relations long strained by differences over who has the authority to appoint bishops in the country.
Complicating matters, CPCA clergy chosen by the Communist Party are sometimes accepted by Rome, while Vatican-appointed bishops are not recognised by the government but are sometimes tolerated.
China is estimated to have about 12 million practising Catholics divided between the official and the underground branches of the Church.