NEW YORK—A former senior U.S. Treasury Department official pleaded guilty Monday to conspiring to give a reporter sensitive financial information about former Trump campaign manager Paul Manafort and others connected to the president.

Natalie Mayflower Sours Edwards, a former employee at the Treasury’s Financial Crimes Enforcement Network, or FinCEN, was arrested in October 2018. Federal prosecutors charged her with one count of unauthorized disclosure of “suspicious activity reports,” known as SARs, filed to FinCEN by banks, and one count of conspiracy.

Prosecutors in New York said the reports pertained to Mr. Manafort, who was chairman of President Trump’s 2016 campaign for several months that year. The documents were also related to ex-Trump campaign aide Richard Gates and the Russian Embassy in Washington, among other topics, according to prosecutors.

Mr. Manafort was convicted of bank, tax fraud and other charges and is serving a 7½ -year sentence in federal prison. Mr. Gates, who pleaded guilty to conspiracy and providing a false statement, was sentenced to 45 days in prison. The cases were part of special counsel Robert Mueller’s investigation into Russian meddling in the 2016 presidential campaign.

The case against Ms. Edwards was part of the Trump administration’s effort to crack down on leaks to journalists. But in a twist, Ms. Edwards was a Trump supporter, motivated by concerns about another unit at the Treasury Department, rather than having any interest in undermining the administration, The Wall Street Journal has previously reported.