Investigators say Wang, 58, was working with her then-fiancé to run a website for Chinese Americans that was spreading propaganda from the Chinese government, or the People's Republic of China (PRC).
Wang agreed to a plea deal, which was already done last month, but was just unsealed on Monday.
It's possible Wang could serve up to ten years behind bars for acting as an illegal foreign agent. She made her first court appearance on Monday and is expected to formally plead guilty in the coming weeks.
"Individuals in our country who covertly do the bidding of foreign governments undermine our democracy," said First Assistant U.S. Attorney Bill Essayli for the Central District of California. "This plea agreement is the latest success in our determination to defend the homeland against China's efforts to corrupt our institutions."
According to federal investigators, the mayor was posting PRC-approved news content on a site called "U.S. News Center."
The documents unsealed on Monday say she would then write back to a PRC official about how many views the content was getting.
Prosecutors write that, "Each time defendant posted to her website at the PRC Official's Direction. Defendant was located inside the United States. Defendant never disclosed on the website that some of its content had been posted at the direction of members of the PRC government."
Wang was elected in November 2022 to the Arcadia City Council, a five-person governing body from which the mayor is selected on a rotating basis.
Earlier this year, Wang's former fiancé and campaign manager was sentenced to two years in federal prison.
Yaoning "Mike" Sun pleaded guilty to one count of acting as a foreign agent to a foreign government. He is now serving a four-year federal prison sentence.
According to the DOJ, Wang and Sun received and executed directives from PRC government officials to post pro-PRC content on their website.
In one example outlined in the unsealed documents, a PRC official sent Wang pre-written news articles, which were then posted on her own website. She reportedly responded to the PRC official on WeChat with a link to the article on her website.
In another example, Wang is accused of making edits to an article, sending the PRC official a link to the article reflecting the requested change, then sending the official a screenshot showing the article had been viewed 15,128 times. In response, the official messaged, "Great!," and Wang reportedly replied, "Thank you leader."
"By her own admission, Eileen Wang secretly served the interests of the Chinese government," said Assistant Director Roman Rozhavsky of the FBI's Counterintelligence and Espionage Division. "Let this serve as a clear warning: individuals who act on behalf of foreign governments to influence our democracy will be identified, investigated, and brought to justice. Protecting the rule of law and the transparency of our democratic process remains at the core of the FBI's mission, and we will continue working alongside our partners to safeguard the integrity of our elections and keep hostile actors from undermining the voices of the American people."