The exclusive report by ABC News said Shahram Amiri's defection was part of a CIA operation to woo Iranian nuclear scientists with family contacts in the United States.
The CIA was said to have approached him through an intermediary in Iran who offered Amiri resettlement in the United States.
ABC said Wednesday it learned about Amiri from people briefed on the operation by intelligence officials.
Those officials termed Amiri's defection as "an intelligence coup," ABC said.
"The significance of the coup will depend on how much the scientist knew in the compartmentalized Iranian nuclear program," said Richard Clarke, an ABC news consultant and former White House counter-terrorism official.
Last year, Iranian Foreign Minister Manouchehr Mottaki and other Iranian officials accused the United States of kidnapping Amiri.