The show, a spinoff of American Idol, will give young contestants the chance to compete for a spot in a five-member pop group.
A total of 20 kids will be chosen to compete, with one kid being booted off the show each week.
"Ryan Seacrest has proven time and again that he is one of the premiere hosts in variety television," said Fox entertainment president Gail Berman.
"As an important member of the Fox family, and the face of American Idol, he is obviously the best choice for the job and we are thrilled to have him join American Juniors."
Seacrest will be joined by a panel of three celebrity judges who haven't been named yet.
Unlike AI, where judges Simon Cowell (search), Randy Jackson (search) and Paula Abdul (search) chose the show's finalists during a nationwide talent search, the American Juniors finalists were chosen by the show's producers, who also traveled the country conducting auditions.
The American Juniors judges will also be kinder in their critiques of the kids, unlike Cowell -- who earned the nicknames "Mr. Nasty" and "The Merchant of Venom" for his often-snide critiques of AI contestants.