Her first appearances are expected to be in print and television advertising for Excellence hair color. The ads were shot recently in Los Angeles and Paris and are to debut in the United States in the fall.
"I'm truly honored to join the confident and inspirational group of women who represent the L'Oreal Paris brand," del Castillo said in a statement.
"We are so proud to welcome Kate del Castillo into our family of L'Oreal Paris spokespeople," said Karen T. Fondu, president of the L'Oreal Paris Division of L'Oreal USA, Inc. "So many have watched Kate grow to be the captivating and talented actress she is today."
The Mexican actress is the daughter of screen icon Eric del Castillo. She has appeared in the film "Under the Same Moon," on the TV series "Weeds" and in the Spanish-language telenovelas "Ramona" and "La Mentira."