Rabbi Menachem Youlus, 50, admitted he had simply made up claims that he personally found and restored Torah scrolls in Europe and Israel.
Prosecutors also said he defrauded the charity he founded and its donors of $862,000 (£545,000).
As part of a plea deal, Youlus faces up to five years in prison.
"I know what I did was wrong, and I deeply regret my conduct," Youlus said in court on Thursday.
According to a criminal complaint, Youlus claimed to have scoured Europe in search of lost or endangered Torah scrolls - the holy Jewish text containing the Hebrew scriptures of the Old Testament.
He distributed the Torahs among American synagogues and communities, sometimes at inflated rates, and put almost one-third of the $1.2m proceeds into his personal accounts.
At a 2004 Torah dedication, Youlus wrote: "I guess you could call me the Jewish Indiana Jones," the prosecutors alleged.
He spent some of it on private school tuition for his children and on personal expenses, prosecutors said.
Youlus, who owns a Jewish bookstore in Wheaton, Maryland, told one prospective buyer that he had personally retrieved parts of a scroll from a metal box at Auschwitz.
If fact, authorities said Youlus rarely travelled abroad during the years he had claimed to go Torah-hunting.
Lawyer Benjamin Brafman said he would seek leniency at sentencing, describing Youlus as "a good man with the best of intentions who ultimately strayed into fraudulent conduct that he now accepts full responsibility for".
Source: BBC News February 3, 2012