The ad features on page three of the Financial Times, in The Times, The Independent, The Guardian, The Daily Mail, The Daily Mirror and the Metro.
It is written in a letter format, signed by Branson, and bordered with Virgin's trademark red.
Branson writes: "I have been personally very committed to finding the right solution to the [Northern Rock's] issues and I'm delighted to tell you that the Northern Rock board has chosen to progress with us.
"Although there is still work to be done and regulatory approval to be received before we can complete the final transaction, with the support of Northern Rock we're working hard with the Government and the Bank of England to deliver our plans for strengthening Northern Rock."
After listing some of the plans that Virgin has for Northern Rock, Branson goes on to thank customers for their support and predicts a successful completion of Virgin's buyout by labelling the bank "ours".
He wrote: "I have the greatest respect for customers and I hope that you will continue to be a valued customer of our new and exciting bank."
Virgin's team was named the preferred bidder for Northern Rock by the bank's board yesterday. The group's offer valued the bank at £200m, considerably less than the £362m the stock market thought it was worth on Friday.
There were signs of wrangling from Northern Rock shareholders about the terms offered by Virgin, with RAB Capital, the holder of 6.7% shares, saying it was opposed to Branson's "cheeky" offer.
Branson's team is planning to rebrand Northern Rock under the Virgin Money banner and pay back £11bn of the estimated £25bn borrowed from the Bank of England immediately.
The group is proposing to inject £1.3bn of equity and borrow the rest of the money it needs from the Royal Bank of Scotland, among others. Virgin also hopes to retain most of Northern Rock's 6,000 staff if its bid is successful.
However, Virgin's takeover is far from secured as the government is expected to clear a second consortium to bid for Northern Rock today.
The group, led by Luqman Arnold, the former boss of Abbey National, was reportedly in discussions with the Treasury, the Bank of England and the Financial Services Authority about its plans last night. An announcement is expected this morning.