The new plan is a policy change from July that reverses a Homeland Security Department ban that cited privacy issues.
A statement from USCIS said the agency will use the fake accounts only “to access social media content that is publicly available to all users of the social media platform,” adding its personnel will respect users' privacy settings and won’t "friend" or "follow" users.
USCIS said it doesn’t proactively monitor social media accounts.
“We use social media information to investigate an existing request for immigration benefits, as part of our background and security check process,” the statement said.
In June, the State Department started requiring visa applicants to give their social media information.
"It is against our policies to use fake personae and to use Twitter data for persistent surveillance of individuals. We look forward to understanding USCIS's proposed practices to determine whether they are consistent with our terms of service," Twitter said in a statement to Fox News.
Dave Maass, a senior investigative researcher for the civil liberties advocacy group Electronic Frontier Foundation, said the new policy "undermines our trust in social media companies and our ability to communicate and organize and stay in touch with people."
There has been bipartisan support for more social media background checks since the 2015 massacre in San Bernardino, Calif., in which 14 people were killed.
The Associated Press contributed to this report.