The actress, 36, was spotted shopping in London’s Chelsea neighborhood today.
Markle has joined Harry in his two-bedroom home at Nottingham Cottage located just behind Prince William and Princess Kate's apartment in Kensington Palace.
Now that Markle has completed her acting commitment to the TV series, it is expected she will move in with Harry full-time and leave Toronto, the city that has been her home base.
The couple is expected to spend the Thanksgiving holiday together as they begin the next chapter of their relationship.
Markle's arrival ahead of the holidays has sparked speculation that an engagement announcement is imminent.
In September, Markle made her first official appearance alongside Prince Harry attending the wheelchair tennis match at the Invictus Games, the Paralympic competition for wounded service members that was founded by Harry in 2014. Several days later, Markle’s mother joined the couple in a luxury box for the the Invictus Games closing ceremony in Toronto.
Royal watchers point to the inclusion of Markle’s mother at such a high-profile event as a sign that an engagement was no longer a matter of if but when.
Markle first publicly declared her love for Harry when she appeared on the October issue of Vanity Fair magazine.
"I can tell you that at the end of the day, I think it's really simple," Markle told the magazine. "We're two people who are really happy and in love."
ABC News' royal contributor Victoria Murphy said the article "shows the strength" of Harry's and Markle's relationship.
"She would have had permission from Kensington Palace to give the [Vanity Fair] interview," Murphy said. "It definitely shows the strength of their relationship and her confidence in their love."
In August, the couple traveled to Africa together on a three-week holiday to celebrate Markle's 36th birthday in Botswana before a romantic visit to Victoria Falls.