The Henry van Straubenzee Memorial Fund helps schools in Uganda, Africa, and was named for one of the prince’s school friends who died in a car accident.
Both Prince Harry and Prince William are patrons of the charity.
The duchess, who is pregnant with her first child, gave a reading from the poem Our Deepest Fear by Marianne Williamson.
The pregnant royal apparently chose the reading because, “it sums up he spirit of what the Henry van Straubenzee Fund does to empower young children," PEOPLE reports.
Harry then spoke to the congregation, highlighting the work the charity does for young girls and giving them an education.
“As my wife said many years ago when working on menstrual health and health education, this is not about periods but potential,” he said, referencing Meghan’s visit to India with World Vision in January 2017 to highlight the importance of breaking the stigma surrounding menstruation.
The 34-year-old royal dad-to-be was very close to Henry van Straubenzee, with the pair both attending Ludgrove prep school.
Prince William counts Henry's older brother, Thomas, as one of his dearest friends. Thomas is the godfather to William's second child, Princess Charlotte.
The royal couple's outing comes after Kensington Palace confirmed both the Duke and Duchess of Cambridge and Duke and Duchess of Sussex would be attending Christmas at Sandringham.
Will and Kate will stay at their nearby home of Anmer Hall with children Prince George, 5, Princess Charlotte, 3, and 7-month-old Prince Louis.
Meghan may also be joined by her mum, Doria Ragland, who has reportedly been invited to join them for Christmas by the Queen.
In the last few weeks, reports have surfaced about tension between brothers William and Harry and their wives Kate and Meghan.
But, a source claimed to PEOPLE that the couple's "enjoyed a memorable first Christmas."
“They really loved Christmas and all had a wonderful time,” the source says. “I think the two women got on — they are definitely not best friends, but it was a really special time for them all to spend together.”
Another source told The Mail on Sunday: “Kate and Harry have always had a very close relationship, but she said things were different.
“Meghan’s a strong character and so is Kate, so it doesn’t surprise me there have been clashes.”
This article was first published by New Idea.