The Metropolitan Police said they cleared the road or protesters within two minutes.
JSO said: "At around 12:30pm today, a group of approximately nine people began marching from Trafalgar Square in support of Just Stop Oil’s demand. All nine were arrested within 30 seconds of stepping on the road."
This is the second day in the row that members of the group have been taken into custody in Whitehall - Monday saw 15 arrests.
Officers are taking demonstrators in based on Section Seven of the Public Order Act, which says a protester can be taken in if they "intentionally or recklessly interfere with the use or operation of any key national infrastructure" or "disproportionately interferes with road transport infrastructure".
Officers are supposed to take into account a person's right to protest before taking them into custody.
It comes as the British Government is facing criticism from the United Nations for long sentences being handed down to JSO members.
💬 "I've just spent 2 minutes marching down Whitehall and I've been arrested."
🚔 @metpoliceuk should be charging the climate criminals with genocide, not arresting ordinary people demanding a future.
🦺 Join us every day, Trafalgar Square, 12pm — https://t.co/7BzUVS0A3x pic.twitter.com/WIwS3O6oPK
— Just Stop Oil (@JustStop_Oil) November 20, 2023
Ian Fry, UN special rapporteur on the promotion and protection of human rights in the context of climate change, has raised with ministers the sentences handed to campaigners who scaled the Dartford Crossing in October 2022.
Morgan Trowland, 40, and Marcus Decker, 34, were jailed for three years and two years and seven months respectively after using ropes and other climbing gear to scale the Queen Elizabeth II Bridge, causing gridlock when police closed it to traffic.
Mr Fry, was quoted by the BBC as saying the sentences were "significantly more severe than previous sentences imposed for this type of offending in the past" and that he was worried about the "exercise of their rights to freedom of expression and freedom of peaceful assembly and association".
But the Prime Minister said it was "entirely right" to hand "tough sentences" to demonstrators who cause major disruption.
"Those who break the law should feel the full force of it," he tweeted.
"It's entirely right that selfish protestors (sic) intent on causing misery to the hard-working majority face tough sentences.
"It's what the public expects and it's what we've delivered."
Last month, Trowland and Decker lost a bid to challenge their sentences at the Supreme Court, the UK's highest court.
In July, the protesters lost an appeal over what their lawyers said were the "extraordinary length" of their jail terms.
In their ruling, the judges acknowledged the "long and honourable tradition of civil disobedience on conscientious grounds" and that the sentences handed to Trowland and Decker went "well beyond previous sentences imposed for this type of offending".
But Lady Chief Justice Lady Carr said the jail terms were "not excessive" and reflected "Parliament's will" under new laws enacted under the Police, Crime, Sentencing and Courts Act last year.
The legislation introduced a new "fault-based public nuisance offence for what obviously will include non-violent protest behaviour, with a maximum sentence of 10 years' imprisonment", the appeal judges said.
Lady Carr said the sentences met the "legitimate" aim of deterring others from such offending.
Just Stop Oil said it would be staging daily marches from Trafalgar Square from November 20 in its bid to get the Government to end new oil and gas licences.
The Met has made nearly 500 arrests of eco-activists associated with the group since October 30, with more than 200 charges.