Father Michele Delle Foglie pinned the mass notices to walls around the town of Grumo Appula, where Sollecito was born, inviting people to attend the memorial mass on Tuesday evening.
Sollecito, thought to have been a high-ranking member of Montreal's Rizzuto crime family, was gunned down while driving his car in May, a "mob hit" which Canadian police said was part of an "ongoing dismantling of the older generation" of the mafia clan.
The notice read: "Father Michele Foglie, spiritually united with family living in Canada and his son, Franco, who is visiting our town, invites the faithful of our community to celebrate a mass in memory of their relative."
A funeral for the 67-year-old was held in Montreal, and attended by 200 people, but his son, Franco, asked for a mass to be held in his hometown.
"The mass does not honour, but remembers him," insisted Father Michele as he sought to calm the controversy.
But Francesco Cacucci, the Archbishop of Bari-Bitonto, issued a ban on the public celebration, describing it as a "serious scandal" while threatening disciplinary action against the priest, La Stampa reported.
A private mass for Sollecito was instead due to be held at 6am this morning.
Italians were outraged in August 2015 after a Rome mafia boss was given a lavish send-off, with his coffin carried through the streets of the capital in a gilded horse-drawn carriage and rose petals dropped from a low-flying helicopter.
The Catholic Church and local authorities were left shame-faced as the event attracted international headlines.