The Radio 1 DJ joins Absolutely Fabulous' Jane Horrocks and Harry Potter actor Jim Broadbent in lending her voice to the kids' favourite.
They will feature in a 21st Century version of the popular BBC series that featured alien characters Tinky Winky, Dipsy, Laa-Laa and Po and ran from 1997 to 2001.
Fearne, 33, who has a two-year-old son, Rex, with husband Jesse Wood and is pregnant with her second child, will provide her famous tones for the Voice Trumpets.
Fearne said: "Teletubbies holds a special place in my heart so I'm honoured to be part of this well-loved TV show. As a mum, I am sure the new series will enthral a new generation of children and I will certainly be watching with my kids."
Programme makers say the re-vamp of the kids' favourite will have a 'refreshed and contemporary look'. New elements include the Tubby Phone, which producers say is 'the Tubbies' new 21st Century gadget'.
The original series has reached more than one billion children and aired in over 120 countries. YouTube postings receive almost 50 million views per month.
Actor and comedian Daniel Rigby will narrate the show. He's best known as a stand-up comic, as well as his BAFTA award winning performance in the 2011 TV film Eric and Ernie.
He said: "It's fantastic that Teletubbies is coming back to Britain's TV screens, and I can't wait for the fun to begin. It's a total thrill to be helping to bring the Teletubbies back to life."