The painting was commissioned by the National Portrait Gallery and, following her suggestion, depicts her natural, not official, persona.
The duchess, who wore a burgundy dress by Whistles, was joined by her husband, the Duke of Cambridge, for a private viewing of the painting on Friday morning before it went on display to the public in the afternoon.
The royal couple spent around 10 minutes looking at the portrait privately then met Emsley and his wife, Susanne, and daughter Marie.
The duchess has been suffering from a rare form of pregnancy sickness but looked well and smiled as she chatted to the artist.
She told him: “It’s just amazing, I thought it was brilliant.”
Prince William also had high praise for the painting, saying: “It’s beautiful, it’s absolutely beautiful.”
The Cambridges later attended a private breakfast reception at the London gallery to mark the unveiling. Among the guests were the duchess’s parents, Carole and Michael Middleton, and her brother and sister, James and Pippa.
I was just about to post this. Its a beautiful painting, but it makes her look older than she actually is. I could see her looking like that in 10 years time!
Forgot to write about me going to see this painting a couple of weeks ago.
Its actually quite big, and has a whole wall to itself. There were about 5-6 other people there viewing it at the time I went. It really does look like a photo. You have to look very closely to see the brush strokes. What I did like is that she looks like she is glowing a little bit, which is pretty and makes her look kind.