The Justice Department says the Iranian government supplied her with housing and computer equipment so she could "disclose US classified information" and conduct research on "personnel that she had known and worked with" during her time in the American intelligence community.
The indictment suggested that Iran had reached out to her at least as far back as 2012.
According to the unsealed indictment, Monica Witt is accused of having defected to Iran in 2013.
Witt served in the Air Force from 1997 to 2008 before separating and becoming a civilian contractor.
The announcement, which also included sanctions on the New Horizon Organization, organization officials, and a company tied to the hacking effort, came on the opening day of a US-led worldwide conference in Warsaw, Poland aimed at boosting pressure on Tehran.
"It is a sad day for America when one of its citizens betrays our country", said the head of the Justice Department's national security division, on what is apparently such a day.
In 2013, Witt traveled to Iran for that year's "Holywoodism" conference.
In a charging document, investigators say the 39-year-old was deployed by the United States to locations in the Middle East to conduct classified counterintelligence operations.
Jay Tabb, the FBI's executive assistant director for national security, said investigators believe Witt shared information that "could cause serious damage to national security", though he declined to provide specific details of the operations she allegedly disclosed.
She defected to Iran in 2013 and is believed to be there now.
She moved into special investigations in 2003, focusing on criminal, fraud and counterintelligence investigations, according to the resume.
Prosecutors say that Iranian intelligence recruited Witt in 2012 when she attended a conference in Iran called "Hollywoodism", organized by Iranian company New Horizon Organization and sponsored by the IRGC.
Iranians march during a rally to mark the 38th anniversary of the Islamic Revolution on February 10, 2017, in Tehran.
The conferences often included an "anti-Western" sentiment and "propagate anti-Semitism and conspiracy theories including Holocaust denial". The New York Times reports she was privy to the real names of both intelligence assets and the U.S. officials who helped recruit them.
U.S. Attorney for the District of Columbia Jessie Liu said that Witt sought to "undermine the U.S. and help the government of Iran", ABC News reports.
Monica Elfriede Witt, a former Texas resident, left the United States military in 2008 after more than a decade of service. That year, an unidentified person contacted her and remarked that she was well-trained. She also reportedly went overseas several times on counterintelligence missions.
The FBI wanted listing says Witt was born in El Paso, Texas and her aliases are Fatemah Zahra and Narges Witt. Witt, a U.S. citizen, defected to Iran in 2013 and is still at large. Iran's nuclear program was the target of the U.S.
Mr Trump has withdrawn the U.S. from the agreement, leading to a foreign policy rift between the United States and the European nations who are party to the deal.
The announcement comes as the USA pressures allies to cut Iran off from the global community by severing economic, financial and diplomatic ties.