The MP took part in the swearing-in ceremony on Monday.
George Galloway has taken his seat in the House of Commons after his by-election victory in Rochdale.
The Workers Party of Britain MP pledged allegiance to the King as part of the swearing-in ceremony all MPs are required to do.
Mr Galloway was accompanied by Alba Party MP Neale Hanvey and Conservative MP Sir Peter Bottomley, the Father of the House, as his sponsors.
He said: “I swear by almighty God that I will be faithful and bear true allegiance to His Majesty King Charles, his heirs and successors, according to law. So help me God.”
Mr Galloway shook hands and had a brief chat with Commons Speaker Sir Lindsay Hoyle before exiting the chamber.
The former Labour and Respect member swept to victory in Rochdale, gaining almost 40% of the vote in a contest mired in chaos and controversy and dominated by the Gaza conflict.
