Showbiz's hottest couple made the announcement in a statement on Friday.
They said: "This year has been such an exciting year for us - England are in the World Cup finals, Victoria's had a second top 10 hit and now we are expecting a new baby. It's fantastic.
"Brooklyn is also really looking forward to having a little brother or sister to play with."
Their son Brooklyn was born in March 1999 and was given that name because the Beckhams stayed in Brooklyn in New York.
David's father, Ted, said: "I haven't spoken to David yet but it's brilliant news if it's true. It would be lovely to have a brother or sister for Brooklyn."