Virgin boss Mr Branson said he would not leave the island he owns to escape the storm, which is becoming one of the largest on record, bringing with it 185mph winds.
The National Hurricane Centre has warned the rainfall could cause life-threatening flash floods, torrential rain, fierce winds and mudslides.
Earlier today the hurricane was upgraded to a Category 5 storm.
Writing on his blog, Mr Branson said: “The devastation that hurricanes can cause cannot be overstated.
“Generally speaking, we have one hurricane in the British Virgin Islands around every 10 years.
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“Fortunately, most of them drift north of us, but this one is coming straight for us, with the eye of the storm heading straight for Necker, Moskito Island and Virgin Gorda.
“Obviously things can change – hopefully they do, as a category five hurricane hasn’t hit the BVI full on before.”
The businessman said Necker Island does have really strong buildings with hurricane blinds, but he admitted almost nothing can withstand the strongest of storms.
He said: “I will be on Necker along side our team, as I have been on the three times we have had hurricanes over the past 30 years.”
Mr Branson urged people in the British Virgin Islands to follow advice and head to shelters when the hurricane arrives.
He said: “I am also concerned for the wonderful wildlife of the BVI, not least on Necker and Moskito, where many flamingos, lemurs, scarlet ibis and other stunning species live.
“Hopefully all people and animals can keep out of harm’s way in the coming days.”
Mr Branson said Hurricane Irma was a sign of the effects of climate change on the world.
He said: “The damage caused by Harvey all over Texas is a tragic and costly reminder that our climate is changing and that we are not doing enough to tackle this enormous challenge.”
Hurricane Irma is expected to strengthen even more over the next 48 hours.