Cosgrove is best known for her work on TV's "Drake & Josh" and "iCarly."
She joins celebrities Gabrielle Union, Hayden Panettiere, Susie Castillo, Vanessa Hudgens, Jennifer Garner, Diane Lane and Emma Roberts as the latest member of the Neutrogena family, the company said.
"My friends and I have always loved the Neutrogena brand and their ability to help inspire confidence. So when I found out I was actually going to be part of the Neutrogena family I was really excited," Cosgrove said in a statement Friday. "I have always looked up to many of the actresses who are already Neutrogena ambassadors, and others are my peers, so it is an amazing honor for me to be part of this incredible group."
"Miranda embodies the youthful and vibrant spirit that has always been part of the Neutrogena brand and we are proud to have her as our newest ambassador," Jim Colleran, president of Neutrogena, said.