Harwood, known to young viewers for his role on shows such as Bear Behaving Badly, and as a co-host with Basil Brush, will become the 35th presenter on the magazine show.
He will replace Joel Defries, who leaves the flagship programme this week.
Harwood, from Blackpool, will take his seat alongside co-presenters Andy Akinwolere and Helen Skelton on 17 January.
He said: "Being a children's presenter is an ambition that I have already fulfilled but becoming a Blue Peter presenter is simply the icing on the cake. I cannot wait to start work with Andy and Helen, wear my badge on screen and tackle some exciting challenges."
Blue Peter, which is screened twice a week, was launched in 1958.