Lovejoy, 41, auditioned for the long-running BBC One children's show 10 years ago, but failed to land the job.
He has now been asked back to fill in for presenter Helen Skelton, who is embarking on a 2,010 mile kayak trip for Sport Relief.
"I auditioned in 1998 when I first started presenting. But I don't think my skills at making things were quite up to scratch," Lovejoy told The Sun. "Despite being turned down then, I am delighted that Blue Peter has asked me on."
Angellica Bell, Radio 1's Scott Mills and Dick & Dom will also reportedly do stints on the educational programme.