Some 300 well-heeled guests and celebrities - including Karen Gillan of "Doctor Who" and "Downton Abbey" star Joanne Froggatt - watched the match at the historic Singapore Polo Club in aid of the prince's charity, Sentebale.
The charity, founded in 2006 by Prince Harry and Prince Seeiso of Lesotho, supports children and young people affected by HIV in Lesotho and Botswana.
HIV and mental health are issues close to the prince's heart following the efforts of his late mother, Diana, Princess of Wales.
Harry, his brother Prince William and sister-in-law Kate have started Heads Together, a campaign intended to remove the stigma surrounding mental health problems.
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The prince also visited the Jamiyah Children's Home where he took part in an "iftar", the breaking of fast during the Muslim month of Ramadan.
He travels on to Sydney tomorrow to promote the 2018 edition of the Invictus Games.
The games, the brainchild of the former soldier prince, feature injured and sick service personnel from around the world.