The powerful Church of Bulgaria has issued a statement expressing "disapproval and disagreement" with Saturday's event, and says the U.S. performer "openly violates" holy Christian symbols.
Tuesday's statement accused Madonna of displaying "a disrespectful and intolerant attitude" to the religious feelings of Christians on her ongoing Sticky and Sweet tour.
Madonna arrives in Sofia after a concert Wednesday in neighboring Romania.
The show at Sofia's Vasil Levski Stadium is expected to be attended by about 50,000 people. Tickets cost up to 150 leva ($110).