The butler, Paolo Gabriele, is charged with aggravated theft for allegedly giving hundreds of secret papers from the pope's personal apartment to an Italian journalist, CNN reported.
Gabriele has admitted leaking the papers -- which included faxes, letters and memos, including some from a high-ranking church official expressing concerns about corruption within the Vatican.
Prosecutors said last month Gabriele acted out of a desire to combat "evil and corruption everywhere in the church."
If convicted, Gabriele could be sentenced to as much as eight years in prison.
Claudio Sciarpelletti, a Vatican computer technician who worked in the Vatican's secretariat of state, is charged with complicity in the alleged crime. If found guilty, he faces a prison term of only a few months.