Trump's former campaign chairman, Paul Manafort, was sent to jail pending upcoming federal criminal trials after Mueller lodged witness tampering charges against him.
Federal prosecutors argued that Manafort posed a threat to the integrity of the court by allegedly violating his bail conditions while under house arrest.
Mueller got more good news in a separate case shortly after, when a Russian company's challenge to the special counsel was shot down by a federal judge.
Concord Management and Consulting is one of three Russian firms and 13 individuals connected to a Russian troll farm that was accused of violating U.S. criminal laws in order to interfere with U.S. elections and political processes. The judge's ruling denied Concord's request to review certain materials in the case.
Meanwhile, an attempt by lawyers for Trump's personal attorney, Michael Cohen, to muzzle Stormy Daniels' firebrand lawyer, Michael Avenatti, was delayed on Friday. Cohen filed an application for a restraining order in Daniels' case to void a hush deal negotiated with Cohen that barred her from discussing an alleged affair with Trump.
The judge in that case said that Cohen's lawyers have not yet demonstrated that "immediate, irreparable injury" would occur without a gag order against Avenatti.
Avenatti has been one of Trump and Cohen's loudest critics, and has become a regular fixture on cable news programs.
The rulings demonstrate continued progress by the special counsel, which is in the midst of a probe into Russian meddling in the 2016 campaign, and increased pressure on the figures in Trump's orbit with deep ties to the president.
"The bottom line on all of this is that [Trump's] certainly going to be feeling some pressure," said David Weinstein, a former federal prosecutor and current white-collar criminal defense lawyer.
The court developments came a day after New York Attorney General Barbara Underwood sued Trump and his family, accusing them of breaking laws through a charitable foundation for "more than a decade."
Trump has recently ramped up his verbal attacks on Mueller, calling his appointment as special counsel "totally UNCONSTITUTIONAL" in a tweet on June 4.
After Manafort was sent to jail, Trump distanced himself from his former campaign chief and appeared to say that it was "very unfair" that ex-FBI Director James Comey and Hillary Clinton had not been jailed.
Weinstein told CNBC Manafort is likely to think more seriously about cooperating with Mueller as a result of the judge's ruling on Friday.