The London firm handed Whyte the sum as part of a ticket-purchase agreement struck in May 2011 and it was subsequently used in the Motherwell-born businessman's deal to buy the Ibrox outfit.
But Whyte, 42, failed to disclose that he has been previously banned from serving as a director.
Now he has been ordered pay back the money to the ticket agency following a hearing at the High Court in London.
Ticketus say they would never have entered into the deal with Whyte - whose own Rangers takeover remains the subject of a police inquiry - had they known about his boardroom disqualification.
A BBC investigation revealed in November 2011 that Whyte was handed a seven-year ban from serving as a director in 2000.
A statement from Ticketus handed to Press Association Sport confirms the company will now seek to recover the cash owed to them by Whyte as well as their legal costs.
It said: "Ticketus can confirm that it has been undertaking legal proceedings against Mr Whyte.
"As part of these proceedings, Ticketus confirms that a Judgment was issued in its favour on Friday, April 5, following a claim it made against Craig Whyte.
"The Judgment relates to Ticketus' claim against Mr Whyte for the serious and deliberate misrepresentations he made during the due diligence process that Ticketus conducted ahead of entering into the ticket purchase agreement with Rangers Football Club plc in May 2011, when Mr Whyte owned the Club.
"Ticketus would not have entered into the ticket purchase agreement with the club if Mr Whyte had disclosed, as required, relevant information concerning his previous seven-year disqualification from serving as a director, and the reasons for the disqualification.
"The Judgment consequently is for damages of £17.7 million, which is the total amount Ticketus invested through the ticket purchase agreement - further interest of around £680,000 and costs have also been awarded. Ticketus will now seek payment of these sums from Mr Whyte. If such payment is not made, Ticketus will enforce its rights to receive such damages."
The statement added: "Ticketus can confirm that during the proceedings Mr Whyte also raised counter-claims against Ticketus. These were rejected in the Judgment.
"The Judgment does not preclude Ticketus from continuing in the proceedings to pursue Mr Whyte under the personal and corporate guarantees built into the ticket purchase agreement as it seeks to recover funds on behalf of its investors."
A spokesman for Whyte told the Scottish Sun that the former Rangers chairman plans to appeal the decision, saying: "Craig is aware of the judgement. It was not totally unexpected as he wasn't given a full trial. He will now be taking his appeal to the High Court."
Rangers went in administration in February last year before eventually being liquidated when Her Majesty's Revenue and Customs rejected a Company Voluntary Arrangement over an outstanding tax bill which Whyte had failed to settle during his 13-month spell as Light Blues chairman.
Charles Green later reformed the club after purchasing its assets from Whyte.
However, Whyte has now threatened legal action against Green and former Rangers director Imran Ahmad - demanding £1million a year for life or 25% of the Ibrox chief executive's shares.
Whyte claims he was the main driver behind the Sevco 5088 company which purchased the assets and business of the company he had put into administration.
Days later Green transferred the assets - which were bought for £5.5million in June last year - to a different company called Sevco Scotland, which then became The Rangers Football Club.
Whyte's main argument appears to be that such a transfer was illegal and he remains the rightful owner of the club's assets.