Flames engulfed Saints Cyril and Methodius Catholic Church in Perth Amboy shortly after 1 a.m. Monday, authorities said.
The fire tore through the roof, and parishioners gathered on Jacques Street to stare at the charred boards that remained as the sun came up. They said morning Mass was always packed at the church, which was described as a longstanding beacon of the community.
Alba Novoa, a parishioner at the church for five years, said her fellow worshipers were in tears when the smoke cleared.
"It's like the families are together every Sunday here," Novoa said.
Investigators are looking into whether any part of the church can be salvaged.
Father Mariusz Zochowski said the church would likely be torn down due to instability, but vowed to rebuild.
"We're small, but we're sure of it. We need help from the community," Zochowski said. "God has a plan for us."
No injuries were reported in the blaze. The cause is under investigation.