The redheaded royal – who will slip to fifth in line to the throne when the baby is born – was in the capital to welcome competitors to the Invictus Games, which kicks off later this week.
Dressed in an Invictus Games shirt, the prince smiled for photographers as he made his way to a games meeting earlier today.
No doubt he's thrilled at becoming an uncle for the second time – and we can imagine Harry will be a pretty fun uncle to have!
When Prince William and Kate welcomed their first child, Prince George, in July last year, cheeky Harry was quick to say he'd bring the laughs to his nephew's life.
Discussing his role in George's life, he said: "To be sure he has a good upbringing and keep him out of harm's way – and make sure he has fun! I'll leave the rest of it to the parents.
"I only hope my brother knows how expensive my babysitting charges are!"
Clarence House announced the Duchess of Cambridge's pregnancy earlier this morning, saying that the royal couple and their families are thrilled by the news.
Unfortunately for Kate, she's suffering from acute morning sickness once again and is being treated by doctors at Kensington Palace.
She was hospitalised with the condition in December 2012 when pregnant with Prince George, remaining in hospital for three days before being released.
Meanwhile, it was work as normal for Prince Harry today despite the exciting family news.
The Invictus Games are a Paralympics-style sporting competition for injured armed forces. They will run from 10 to 14 September at Queen Elizabeth Olympic Park in London.
Celebrities congratulate Kate and William on their second baby news!
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