The No Doubt singer already fronts apparel line Harajuku Lovers and has now teamed with department store Target to create companion brand Harajuku Mini.
Stefani told Women's Wear Daily: "Harajuku Mini is a dream come true. I've always wanted to do a cool children's fashion line inspired by the supercute and playful kid's clothing you find in Japan.
"Target has given me the creative freedom to design kid's clothing that is different than most anything you usually see out there with great quality, attention to detail and most of all, available at amazing prices."
Harajuku Mini, which is named after Stefani's 2004 solo track 'Harajuku Girls', will be available in stores from November 13.
The singer also owns a third fashion company, L.A.M.B., which she founded in 2003 to manufacture shoes, handbags and a signature fragrance.
Stefani recently revealed that she has no plans to record a follow-up to her platinum-selling 2006 solo album The Sweet Escape and will instead devote all her efforts to No Doubt.
No Doubt are apparently close to finishing work on their sixth studio album.
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Watch Gwen Stefani perform 'Harajuku Girls' below: