Father Cornelius Breslin is accused of writing checks to himself from the bank accounts of St. Mary's and Saint Patrick's parishes, where he is pastor.
The investigation began after the Attorney General's office received a report of suspicious financial activity from the Diocese of Wilmington.
The Attorney General's office says its investigation revealed that Father Breslin wrote checks to himself for more than $358,000 from church accounts over the period from July, 2009 through August, 2010, and that he deposited these funds into an account at another bank.
Breslin turned himself in to Capitol Police in Wilmington on Wednesday.
An investigation into this case continues.