The Foreign Secretary said he would abide by NHS track and trace rules and stay out of public for two weeks.
Mr Raab said he will work remotely for the 14 days amid diplomatic challenges with the US over the election chaos.
The 46-year-old was twice tested for the virus during the first wave, but both came back negative.
'The Foreign Secretary was today informed that an individual with whom he has been in recent close contact with has tested positive for coronavirus,' the spokesman said
The UK is entering a difficult phase in its relationship with the US after Donald Trump plunged the nation into crisis by falsely claiming victory and mounting legal challenges.
Not only have there been calls to criticise the president's behaviour, but Britain is under pressure to improve relations with Joe Biden, the Democratic challenger who is favourite to lead the White House.
Mr Raab's spokesman said: 'The Foreign Secretary was today informed that an individual with whom he has been in recent close contact with has tested positive for coronavirus.
'In line with Government regulations and NHS track and trace rules, the Foreign Secretary has taken immediate steps to self-isolate for the required period. He will continue to work remotely during this time.'
Mr Raab said he will work remotely for the 14 days amid diplomatic challenges with the US over the election chaos (file photo)
The Foreign Secretary, along with Boris Johnson, has refused to criticise Trump for claiming there is a 'fraud on the American nation' and saying he would use the US Supreme Court to get vote counting stopped.
Mr Raab said 'we need to be patient' and await the outcome of the election, insisting 'we have full confidence in the checks and balances of the US system to produce a result'.
He insisted he would not get 'sucked in' to the debate around Mr Trump's actions, which have been widely criticised as threatening democracy itself.
Mr Raab has also faced pressure in the UK this week, with travel bosses urging him to lift the blanket ban on 'non-essential travel' and allow international holidays.
The Foreign Secretary, along with Boris Johnson, has refused to criticise Trump for claiming there is a 'fraud on the American nation' and saying he would use the US Supreme Court to get vote counting stopped
Nearly 70 travel companies have asked the Foreign Secretary to allow travel to foreign destinations that are not high-risk in an effort to keep the travel industry moving and unlock flights to countries outside of Europe.
The new rules, which ban all outbound international travel, apart from in exceptional circumstances, are set to be introduced as of today.
Travel from England to other parts of the UK - apart from for work - will also be banned as part of the new rules, which are set to last until December 2
Passengers rush to a very busy Heathrow Airport on the last day before national lockdown
In a letter to Mr Raab, travel bosses point out that advice from the Foreign, Commonwealth and Development Office (FCDO) currently states that travellers wishing to fly to non-exempt countries must do so with 'inadequate or no insurance'.
The letter, seen by The Daily Telegraph, reads: 'We all either work for or represent specialist and long-haul tour operators, and have all had to make valued members of staff redundant.'
Earlier this week, England faced a fresh round of holiday chaos ahead of strict new winter lockdown rules which will outlaw winter getaways.
The new rules, which will see both international travel and travel inside the UK banned for a month, sparked a stampede of people rushing to the departure gates before they were slammed shut to all but a handful of travellers.
What are the exemptions for travel?
According to the Foreign, Commonwealth and Development Office (FCDO), going on holiday will be banned as of Thursday - with no exceptions.
The ban is currently set to last until December 2.
Under the new rules people cannot travel internationally or within the UK, unless for work, education or 'other legally permitted exemptions'.
Overnight stays away from primary residences will also not be allowed, except for specific exceptions including for work.
Meanwhile top tour and flight operators revealed plans to cut huge swathes of flights due to the new rules - with some already announcing plans to offer full cash refunds to customers.
Other top travel industry chiefs called for more support to help the struggling tourism trade - which faced similar restrictions back in March.
Following the announcement, TUI, the world's largest travel and tourism company, revealed its customers will be offered a refund for holidays dashed by the new lockdown laws, while easyJet chiefs called for support for the travel industry.
In a statement, a spokesperson for TUI said: 'Following the recent announcement about additional restrictions in England from 00:01 on Thursday 5 November all TUI holidays between Sunday, November 1 and Wednesday, November 4 are currently due to operate as planned.
'Customers due to travel before Thursday are able to amend their holiday to a later date for free.
'We understand that holidays abroad (for those living in England) are unable to take place from 00:01 on Thursday, November 5.
'As soon as we have more information we will be updating customers as soon as we can.
'If holidays are unable to take place, customers will be notified and offered the option to amend with an incentive, receive an ATOL-protected refund credit note with a re-booking incentive, or cancel and receive a full cash refund within 14 days.
'Customers currently on holiday can continue to enjoy their holiday as planned.'
Elsewhere Jet2 said it was planning to continue as normal until the lockdown deadline.
A spokesperson said: 'We are planning to operate as normal between now and Wednesday, November 4, so customers wanting to get away from the cold and gloom can still book and travel as normal.'