The golden couple of Spanish cinema have a two-year-old son Leonardo, who was born in January 2011.
The 38-year-old actress and her 43-year-old husband Javier Bardem, divide their time between homes in their native Madrid and Los Angeles.
The pair of Oscar-winners have been friends for many years but only tied the knot in July 2010 in The Bahamas in a low key ceremony. No photos were ever released of their wedding.
The couple are notoriously private and have never allowed photos to appear of their son.
According to her publicist the actress, who previously dated Tom Cruise, is “extremely happy and very excited” about the news.
The actress has spoken about how becoming a mother to Leo changed her life.
She described now “From the first second, you feel so much love.
“That's the best way I can describe it. It transforms you completely, in a second.
“Nature is very wise and gives you nine months to prepare, but in that moment, when you see that face, you are transformed forever,” she told one magazine.
Monica Cruz, the actress's younger sister, who is a an actress and model for Mango and Agent Provocateur, announced her own pregnancy by artificial insemination last month.