A tiny independent church in Woodstock calls itself after the venerated nun.
But the Roman Catholic Archdiocese of Atlanta and the Missionaries of Charity, the group founded by Mother Teresa, have sued, saying they have exclusive rights to her name.
Matthew Coles, attorney for the archdiocese and the Missionaries of Charity, said Mother Teresa was a Roman Catholic and in union with the Roman Catholic Church.
"The defendants are neither," he said.
The suit claims Woodstock's Mother Teresa Parish of the Old Roman Catholic Church in North America uses her name to attract members and contributions, but its practices conflict with the teaching of the Roman Catholic Church. That harms the Roman Catholic Church's reputation, it says.
Mother Teresa won the Nobel Prize in 1979 for her work among the poor in India. She died in 1997.
The Mother Teresa Parish is affiliated with about 70 other independent Catholic churches, members of a group based in Louisville, Ky., who call themselves "Old Catholics."
Their Masses follow the Roman Catholic style, but their beliefs differ on issues such as infallibility of the pope, and the veneration of Mary and the saints.
Bishop Richard Roberts, a former Episcopalian ordained by the Catholic Church of North America, helped start the Mother Teresa Parish. He said she was an example for Christians and that the Roman Catholic Church can't copyright the ideals she represents.
"I didn't think that a church per se can own a name," Roberts said. "Whether someone is doing good works or not shouldn't be locked into an association with one denomination or another."
Bishop Roberts and Father Kieran Pavlick have from a dozen to 20 worshippers at Saturday and Sunday services at their modest chapel in a strip shopping center. Both men support themselves with jobs outside the church.
Before taking legal action, the archdiocese asked the church to drop the name, Coles said. The lawsuit doesn't seek damages; it asks only that the church stop using Mother Teresa's name and pay the Roman Catholic Church's legal fees.
Roberts said they want to stick with the name.
"It's not that we are taking Mother Teresa's name in vain and trying to make her out in some bad light. We are hoping we can work it out, but you're never sure," he said.