Trump hailed Sir Winston as a “real ally” and appeared to make good on an agreement to return the former prime minister’s likeness to the famous office within hours of being sworn in.
Its renewed presence was noticed as Trump signed his first orders as the 45th president of the United States.
Former Ukip leadership candidate and Breitbart London editor Raheem Kassam took credit for the return of the bust.
“When I met Trump as President elect I asked him to return the Churchill bust to the Oval Office,” he wrote on Twitter.
The claim was branded “toe-curlingly pathetic”.
Trump also dismissed allegations that he removed a bust of civil rights champion Martin Luther King Jr, which replaced that of Churchill during Barack Obama’s presidency.
The newly-elected president told a press conference at the CIA headquarters in Virginia: “I would never do that because I have great respect for Dr Martin Luther King - but this is how dishonest the media is.”
He explained that a cameraman had blocked the bust of Dr King from view during the photocall, the Press Association reported.
A pool media report has confirmed that the bust of Dr King was obscured by a door and a Secret Service agent during the Oval Office photocall, the Associated Press reported.
Trump told the press conference: “I think most of us like Churchill. He doesn’t come from our country but had a lot to do with it, helped us, a real ally.”
The sculpture of Churchill’s face is said to be a replica of one given to 1960s leader Lyndon B Johnson, which is thought to be placed in the White House residence.
The Oval Office bust was originally provided in July 2001 by then Prime Minister Tony Blair as a loan to President George W. Bush, the Washington Post reported last year.
Since its removal after the Bush administration, it has been kept at the British embassy in Washington.
Reports of Churchill’s removal prompted protests from British figures including Foreign Secretary Boris Johnson, who in turn was criticised when he blamed the swap on Obama’s “ancestral dislike of the British empire”.
He explained at the time: “When I was elected as president of the United States, my predecessor had kept a Churchill bust in the oval office.
“There are only so many tables where you can put busts, otherwise it starts looking a little cluttered.
“And I thought it was appropriate and I suspect that most people here in the United Kingdom might agree, that as the first African-American president, it might be appropriate to have a bust of Dr Martin Luther King in my office to remind me of all the hard work of a lot of people who would somehow allow me to have the privilege of holding this office.”
After meeting Trump in November, former Ukip leader Nigel Farage said he was “especially pleased at his very positive reaction to the idea that Sir Winston Churchill’s bust should be put back in the Oval Office”.