The 34-year-old will help Alterna Haircare brand grow worldwide - particularly in salons and retail stores, People magazine reported.
Holmes will also appear in advertisements in March 2013's women's beauty, lifestyle and salon trade magazines.
"I'm really proud to be a part of this company - not only because the products are incredible, but because their 'accessible luxury' and 'free of' philosophy really speaks to me," she said.
Holmes said that the products were good for her hair and earth therefore she felt good using it.