Businessman Selman Turk is being sued by fellow Turkish national Nebahat Isbilen, with a trial in London expected to begin in November.
Isbilen alleges Turk, her former adviser, misled her over a STG750,000 payment made to the then-duke in 2019, which was later paid back.
Turk denies dishonesty and made a bid to be allowed to call Mountbatten-Windsor to give evidence at the trial.
In a judgment on Friday, Justice Adam Johnson agreed and allowed Turk to rely on a witness summary, as well as giving him permission to seek to call evidence from Mountbatten-Windsor.
Witness summaries outline the potential evidence a party in proceedings believes a witness could give when they are unable to get them to get a witness statement from them.
He said: "Given the seriousness of the allegations, both on their own terms and in light of their wider impact, fairness requires that Mr Turk should be afforded an opportunity of putting forward his own case, using the evidence he considers relevant and material."
The judge said although Turk had been late to seek to rely on evidence from the former duke, the evidence from is "limited in scope" and can be accommodated in the 11-week trial.
Lawyers for Isbilen have previously told the court that tens of millions of her funds had been misappropriated, with Turk then failing to explain where the money had gone.
The High Court was also previously told by lawyers for Isbilen that "money was used for purposes unconnected with Mrs Isbilen, e.g., substantial sums were paid to Prince Andrew, Duke of York, and to Sarah, Duchess of York".
In Friday's ruling, Justice Johnson said it "has long been Mr Turk's case" that the payment was made on Isbilen's own accord as she thought Mountbatten-Windsor could help with her husband, who she claims has been the victim of political persecution in Turkey.
The court heard in 2023 there had been a "settlement" between Isbilen and the then-Duke and Duchess of York.
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