"We can confirm that Archie is going to be a big brother," the spokesman said, referring to the couple's son. "The Duke and Duchess of Sussex are overjoyed to be expecting their second child."
The couple released a black and white image of them under a tree, all smiles, with Markle showing signs of pregnancy.
Meghan and Harry, who is Queen Elizabeth II's grandson, quit frontline royal duties in March last year and now live in California.
Prince Harry and his wife, Meghan, the Duke and Duchess of Sussex, are expecting their second child since their marriage nearly three years ago.
The couple are "overjoyed," a spokesperson for the family said Sunday. Harry and Meghan's first child, a son named Archie, who will turn 2 in May, is seventh in line to the throne. Their charitable foundation, Archewell, is named after their son.
Meghan revealed that she had suffered a miscarriage in July, writing about the loss in a New York Times opinion article in November. "Losing a child means carrying an almost unbearable grief, experienced by many but talked about by few," she wrote.
The couple have made numerous moves to protect their privacy since the birth of their son, including stepping back from their duties as members of the royal family and moving out of England.
Meghan also won a privacy suit Thursday against Associated Newspapers — the publisher of the Mail on Sunday and MailOnline — for publishing excerpts of a letter she wrote to her estranged father, Thomas Markle.
Judge Mark Warby wrote in a ruling that Meghan "had a reasonable expectation that the contents of the letter would remain private" and that the articles had "interfered with that reasonable expectation