Emirati Lebanese shipbuilder Privinvest wanted to drag Nyusi into a $3.1-billion lawsuit brought by Mozambique, which accuses it of paying bribes to officials and Credit Suisse bankers.
London's High Court has yet to rule on the case following a trial last year. Mozambique settled with Credit Suisse's new owner UBS on the eve of the trial in October.
Shortly before last year's trial began, the High Court ruled that Nyusi had not been properly served with Privinvest's lawsuit and that he was entitled to immunity as a head of state.
Privinvest wanted to sue the Mozambican president for allegedly accepting $11 million in campaign payments from Privinvest, which says the payments were lawful.
The company says if the court finds the payments unlawful, Nyusi should contribute to any damages it may be ordered to pay.
But the Court of Appeal ruled on Thursday that Nyusi was not properly served with the case.
Judge Julian Flaux also said in a written ruling that Nyusi "has immunity from the jurisdiction of the English courts whilst he is the head of state of Mozambique."
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