The former UKIP leader will provide political analysis for the main channel, and the Fox Business Network's daytime and primetime programmes.
Mr Farage has been one of the UK's most prominent supporters of US President Donald Trump and appeared alongside him during his election campaign.
He was the first UK politician to meet Mr Trump after his win in November.
It comes shortly after he was given his own nightly show on UK radio station LBC.
Mr Farage travelled to Washington for Mr Trump's inauguration on Friday.
After the ceremony he tweeted his approval saying: "A very strong speech by @POTUS. He means it."
He also appeared on Fox Business to comment on the inauguration. He said: "Listening to the speech today, this is a political revolution and it's very exciting."
Mr Farage has said he wants to be a "bridge" between the UK and Donald Trump's US administration.
The US president tweeted in November that Mr Farage would make a good British ambassador to the US but Downing Street rejected the suggestion, saying there was "no vacancy".

North Wales Chief Constable Mark Polin said the police were likely to "bear the brunt" of further cuts to the Home Office budget by 2020.
Dyfed-Powys Commissioner Christopher Salmon has urged ministers to take rural needs into account when changing the police funding formula.
The Home Office has said no decisions have been taken beyond this year.
Mr Polin sent an email to North Wales force employees responding to a UK government statement that by 2020 the Home Office would have only half of the funds it had in 2010.
He said: "The police service represents the largest slice of the Home Office budget and therefore it is a realistic assumption that we will bear the brunt of any such reduction.
"Indeed, a further cut of between 25% and 40% is being suggested and you won't need me to tell you how this would represent a significant challenge for us (and other forces) to achieve in addition to that we have already saved and plan to save."
North Wales Police and Crime Commissioner Winston Roddick said the force had achieved "tremendous success during a time of great challenge".
"Further cuts are inevitable and will put greater pressure on staff and resources," he added.
Meanwhile his Dyfed-Powys counterpart Christopher Salmon - supported by three of the region's Conservative MPs - called for "fair funding" for rural areas in the current consultation over changes to the Police Allocation Formula, which the Home Office says needs updating.
In a letter to ministers, Mr Salmon and the MPs - Chris Davies, Glyn Davies and Simon Hart - claimed the new formula would favour heavily-populated urban centres and make little allowance for the extra costs associated with policing rural areas.
"We urge, on behalf of the people of Dyfed-Powys, that the government recognises the limitations of urban-based statistics in describing rural areas," the letter said.
"We also urge that the government does not neglect the additional cost of providing services to those areas, from additional fuel costs to the additional infrastructure required to maintain a reasonable emergency response."

The Dons loaned Smith, 21, to United in July and he has five goals this season.
Scotland Under-21 cap Smith made his Aberdeen debut in 2012 and has scored four times in 89 appearances for the Pittodrie side.
"It's a brilliant acquisition for us," boss Jack Ross told St Mirren's official website.
"Cammy is a really good player and someone I didn't think we'd be able to get because he was at Dundee United.
"He's a good, mature boy and I think he'll be a good fit and gives us another option in the attacking area."
Championship bottom side St Mirren host Falkirk on Saturday.
Nigel Farage has been hired as a commentator for American TV network Fox News, the broadcaster has announced.
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Senior figures at two Welsh police forces have raised fears about their funding in the coming years.
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St Mirren have signed forward Cammy Smith on loan for the rest of the season after Aberdeen ended his spell with Dundee United.