Meghan said it is "very nice to be back in the UK" as she took to the stage in front of 2,000 young leaders in Manchester on Monday.
But while the Duchess of Sussex appeared comfortable and confident, the Duke did the opposite at the One Young World Summit.
As well as looking "ill-at-ease", Harry responded to Meghan's words by "looking down and then upward with what looked like a sigh", according to body language expert Judi James.
She said: "Harry himself appeared much more ill-at-ease on his return to the UK, responding by looking down and then upward with what looked like a sigh.
"His anxiety rituals were frequent, suggesting a desire to self-reassure as he touched his clothing and checked his tie several times."
Meghan Markle and Prince Harry in Manchester
MOLLY DARLINGTON
Prince Harry and Meghan Markle
MOLLY DARLINGTON
Prior to Ms James' comments to MailOnline, Meghan opened her speech by saying: "Good evening everyone, it is very nice to be back in the UK and it is very nice to be back with all of you at One Young World."
She went on to tell the youngsters: “You are the future… you are the present.”
Meghan also revealed her “nervousness” and the “pinch-me moment” of her first summit.
She said: “I was the girl from Suits, and I was surrounded by world leaders, humanitarians, prime ministers and activists."
By the 2019 summit, she said it was “fair to say, my life had changed”.
Talking about motherhood, Meghan said: “My worldview had expanded exponentially, seeing the global community through the eyes of my child [Archie, born 6 May 2019], and I would ask what is this world he would come to adopt, and what can we do, what can I do to make it better.”
But the Duchess has faced criticism as, although her speech was billed as one about equality, she appeared to talk more about herself.
Royal commentator Kinsey Schofield appeared on Breakfast with Eamonn and Isabel to discuss the speech on Tuesday morning.
She told GB News viewers: "The irony that, when Meghan Markle is supposed to be giving a speech on equality...
"The UK, you're seeing your third female Prime Minister. It's like: 'We got it, we get this.'
"I didn't hear anything about equality whatsoever. I just heard Meghan talking about Meghan.
"There should have been a focus on spotlighting individuals in the audience who had done unique things. She didn't challenge anybody.
"There were so many routes she could have taken but it seems so fixated on her brand and what people think about her, and how to control the narrative, that she misses huge opportunities to really be this change-maker, this thought-leader that both Harry and Meghan want us to think they are."