Mr De Plata's lawsuit is the 14th filed against Guam's Catholic Church since the government in September removed the statue of limitations that prevented historical cases from being prosecuted.
Mr De Plata also told the Pacific Daily News that a then-seminarian, Anthony Apuron, was present when the abuse took place.
Mr Apuron, who was the highest leader of Guam's Catholic Church for 30 years, is now undergoing a canonical trial in the Vatican over multiple allegations of historical sexual abuse.