Three-year old Madeleine went missing from the Praia da Luz resort in the southern Portuguese region of the Algarve eight days ago. Investigators believe she was kidnapped.
"Last Thursday evening a little girl called Maddy was taken from the family hotel room in the Algarve in southern Portugal. As I'm sure you understand, we need to do everything possible to help the police with their enquiries in finding her," Beckham said.
Madeleine disappeared from the McCann's holiday apartment while her parents were at dinner.
No arrests have yet been made relating to the disappearance of Madeleine, whose fourth birthday is on Saturday.
"If you have seen this little girl please could you go to your local authorities or police and give any information that you have," said Beckham, holding up poster with a photograph of Madeleine.
Manchester United's Cristiano Ronaldo and Chelsea footballers John Terry and Paulo Ferreira have also made appeals for Madeleine's safe return.
Police in Portugal have begun to scale down local searches, saying the case has now become an international investigation.
"Please, please help us, thank you," said Beckham.