The lawyer was previously seen at the peer's house on Friday, and was inside when police officers were searching the property throughout the afternoon and evening
Adrian Darbishire KC arrived at the former cabinet minister's house shortly before midday wearing black-rimmed glasses and a navy blue jacket and jeans.
He left the property around 90 minutes later.
The lawyer declined to comment as he left the house, including on whether he represents Lord Mandelson.
But he did confirm his identity.
He was previously seen at the peer's house on Friday, and was inside when police officers were searching the property throughout the afternoon and evening.
This comes after the Met confirmed it was investigating the former peer over allegations relating to files appearing to show him sharing government information with paedophile financier Jeffrey Epstein during the financial crash.
Mandelson has yet to speak publicly on the matter.
Mr Darbishire KC is described as "a superb tactician and a powerfully persuasive advocate" on the website of QEB Hollis Whiteman's, where he is listed as joint head of chambers.
The barristers' chamber says the lawyer "specialises in the defence of professional individuals charged in criminal and disciplinary proceedings arising in connection with their work", adding Mr Darbishire "has vast experience of the full gamut of offences in this field and creatively defends against them with apparent ease".
Police officers left two homes linked to former US ambassador Peter Mandelson on Friday evening after spending hours carrying out searches and taking boxes away.
The two addresses, located in Wiltshire and Camden, north London, form part of a misconduct in public office investigation relating to Mandelson's links to Jeffrey Epstein.
Images emerged on Friday showing several police officers arriving at Mandelson's Camden address, close to Regent's Park, with files in hand, moments before both appeared to enter the property.
The authorities left the plush London pad shortly after 8pm.
One could be seen carrying a white cardboard box and another with a blue plastic one. Reporters’ cameras flashed as they drove away in cars that had been parked outside the building.
Issuing an update on their investigation, Deputy Assistant Commissioner Hayley Sewart said the investigation will take “some time” to conclude.
A statement read: ”I can confirm that officers from the Met’s Central Specialist Crime team have carried out searches at two addresses, one in the Wiltshire area, and another in the Camden area.
“The searches were related to an ongoing investigation into misconduct in public office offences, involving a 72-year-old man.“He has not been arrested and enquiries are ongoing.
“This will be a complex investigation requiring a significant amount of further evidence gathering and analysis. It will take some time to do this work comprehensively and we will not be providing a running commentary.”
