Griffith, 52, was clean for six years, then she was injured in a skiing accident a year and a half ago. Three operations on her knee required the actress to start using narcotics.
Banderas, 49, tells Ellen DeGeneres, "In March, she came to me and said, 'I'm feeling a little bit weak in my determination for this... so I just thought to go to rehabilitation by myself.'" The actor says their whole family is behind her, "this particular time more than ever," adding, "I'm very proud of her."
Banderas also has advice for families struggling with addiction. "Don't get embarrassed, just confront this problem head-on. And don't hide from that because there is a beautiful gift at the end of this tunnel, and it is the person that you love back, and that is what I am searching for."
Antonio Banderas' interview airs Wednesday on "The Ellen DeGeneres Show."