In his role as Commodore-in-Chief Small Ships and Diving, he spent the morning at the naval base in Devonport.
'The Happy Prince' lived up to his reputation as he chatted to staff who were no doubt keen to find out how his newborn nephew Prince George is.
Harry, who is dating blonde socialite Cressida Bonas, revealed that the birth of the infant Prince meant the pressure was off him to have children.
Resplendent in his Dismounted Service Uniform of the Blues & Royals with Army Air Corps beret, the RAF Apache co-pilot reviewed the parade of the Marines of 1 Assault Squadron.
Scores of people had gathered in the stands to watch the Prince in action. He spoke to some of the Royal Marines in the parade before taking the Royal Salute and the Royal March Past.
He then attended a reception for the servicemen and servicewomen and their families, engaging warmly with both adults and young children alike.
The 28-year-old was due to officially declare the centre open with the unveiling of a plaque and his visit would culminate in a photograph with the Royal Marines.
Although he is currently focusing on his military career, the fourth in line to the throne also dedicates his time to raising awareness and support for the Armed Forces.
Prince Harry along with Prince William and Kate Middleton set up The Royal Foundation of The Duke and Duchess of Cambridge and Prince Harry in 2009 and it became fully operational in 2011.
One of the charity's main focuses is working to promote "the welfare of those who are serving or who have served their country in the Armed Forces".
Harry's recent tour to the US saw him promote these causes that are close to his heart.
"He is a soldiers' soldier and will bring a spotlight on what's being done to help these outstanding men and women," said his press secretary Jamie Lowther-Pinkerton ahead of the tour.