In a statement, Harry said: “Thomas the Tank Engine has been a comforting, familiar face to so many families over the last 75 years – entertaining, educating and inspiring children on important issues through exciting stories and characters.
"I certainly have fond memories of growing up with Thomas & Friends and being transported to new places through his adventures. I am very proud to have been asked to take part in this special episode. I wish Thomas & Friends a very happy anniversary," he added.
In the 22-minute special, Thomas travels to London to take Sir Topham Hatt, one of the show's main characters, to Buckingham Palace to receive a special honour from the Queen.
As expected, the loveable train seemingly gets into trouble along the way and finds himself arriving to meet the Queen in a very messy way.
Joining Harry on the project is British actress Rosamund Pike, who voices a very important looking train called Duchess of Loughborough, which transports Her Majesty and Charles.
Speaking of the honour, the Gone Girl actress said it was a privilege to be part of the 75th anniversary and play such a “lovely” and “warm” character.
"I take it as a big responsibility to play Duchess who is a lovely, warm, bubbly sort of effervescent engine that I am incredibly drawn to because she is very anxious to get things right," Rosamund said.
The special episode will reportedly be screened in the US on Netflix on May 1 and in the UK on Channel 5 on May 2, followed by the rest of the world.