The fire early Sunday raced through the First Universilist Church on Route 25 in Southold.
The Southold Fire Department and other area departments responded and extinguished the blaze.
The building was unoccupied at the time of the fire.
The Suffolk County Police Arson Squad responded and assisted in the investigation.
The cause of the fire is under investigation, but is not belived to be suspicious.
Rev. Jeffrey Gamblee told Newsday that the church was established in 1837 but the building on Route 25 was constructed in 1860.