Joel Defries, 23, will join current host Andy Akinwolere and fellow newcomer Helen Skelton on the long-running BBC children's show.
The trio will kick off a new series on September 23.
Speaking about landing the job, Defries said: "Being the presenter of Blue Peter is one of the finest jobs in the world.
"I wake up every day thinking 'I can't believe this is happening'. I have never been so happy and can't wait to see what other adventures Blue Peter has lined up for me."
Skelton, 25, commented: "We've done so much exciting stuff for the new series - I'm covered in bruises already, but I'm early for work every day!"
The show's editor Tim Levell said: "In our 50th birthday year, we want Blue Peter to be as fresh and as relevant to children as ever, and we believe that our two new presenters will really help us achieve that aim.
"Helen Skelton and Joel Defries, will be as popular with today's children as John Noakes, Peter Purves and Valerie Singleton were in the past."