According to Vatican spokesman Greg Burke, Chinese Catholic bishop Peter Shao Zhumin was taken by authorities in May.
The bishop's family has not been told why he was seized or where he has been taken to.
China and the Vatican have not seen eye to eye on who can appoint bishops in the country which has led to a strained relationship.
Burke said the Bishop Peter's detention has worsened efforts to reach an understanding with the Chinese authorities on the status of the Church in China.
He added: "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."
Catholics fear that that Bishop Peter may be pressured by the authorities to pledge his allegiance to the Communist Party instead of the Vatican.
