According to People, the former Bachelorette star will begin filming the new season of the ABC show later this year.
"I can't wait to get on that bus again and make a difference! I have been such a fan of the show for years," she is quoted as saying.
"I watched the designers and thought, 'Wow, what an incredible opportunity that would be'. And here I am one of those designers!"
The interior designer made a guest appearance on the series earlier this year, helping to design a children's bedroom, and later admitted that she would love the opportunity to appear on the show again.
Harris - who added that she is "so excited" on her Twitter account - and Ty Pennington will reportedly be joined by Xzibit and Leigh Anne Tuohy.