Doria Ragland is believed to have landed in London on Thursday, according to Good Morning America.
She and Meghan’s dad, Thomas Markle, are expected to meet the Queen in the next few days.
They will also spend time with Prince Philip, Prince Charles and wife Camilla and the Duke and Duchess of Cambridge.
Omid Scobie, Royal contributor, told GMA: ‘Doria will be meeting Harry and Meghan’s nearest and dearest while she’s here, including close friend Jessica Mulroney, who arrives on Monday.
Mr Markle and Ms Ragland divorced when Meghan was just six years old but they are both due to attend the wedding on May 19.
Meghan’s dad has started preparations for his journey to London, where he will walk his daughter down the aisle at Windsor Castle.
The former lighting director, 73, was pictured last night in his silver Volvo heading to the airport, after being spotted browsing articles about the Royal Wedding earlier this week.
He has previously said that he would ‘love’ to give Meghan, 36, away on her big day, telling The Mirror: ‘I’m very pleased. I’m delighted.’
A royal spokesman said: ‘Prince Harry and Ms Markle are very much looking forward to welcoming Ms Markle’s parents to Windsor for the wedding.
‘Mr Thomas Markle and Ms Doria Ragland will be arriving in the UK in the week of the wedding, allowing time for Prince Harry’s family, including The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall, and The Duke and Duchess of Cambridge, to spend time with them before the big day.
‘Both of the bride’s parents will have important roles in the wedding. On the morning of the wedding, Ms Ragland will travel with Ms Markle by car to Windsor Castle.
‘Mr Markle will walk his daughter down the aisle of St George’s Chapel.
‘Ms. Markle is delighted to have her parents by her side on this important and happy occasion.’