Charles told guests at a reception in Qatar that the Arabic language “goes in one ear and out the other”.
But an aide later disclosed that the Prince has been having private tuition for more than six months.
Charles’s new skill could help his desire to encourage dialogue between different religions, as he would be able to read the Koran in its original form.
Charles, 64, was in Doha at an event for Qataris who have attended British universities. He told guests: “You all speak such good English.”
Dr Mohammed Bin Saleh Al-Sada, chairman of the Qatar-UK Alumni Network and the country’s energy minister, asked the Prince if he spoke any Arabic.
Charles replied: “I tried to learn it once but I gave up. It goes in one ear and out the other.”
Dr Al-Sada told him: “It’s never too late to learn.”
An aide confirmed afterwards that Charles has been taking lessons.