The longtime pair, who split up last year, showed no hard feelings as they embraced just before stepping onto the green carpet before a large crowd in London's glittering Leicester Square.
"I really like it. We're friends. It's good to see him," said Diaz, 34, who wore a long black Chanel dress.
"It's great having him around. We've not been able to sit down and have a chat yet we've been so busy," said Diaz, who voices Fiona, the princess.
Timberlake, 26, who voices the future King Arthur, said of the premiere: "It's massive, it doesn't get any bigger than this I don't think."
Asked about his love life, Timberlake joked: "I'm allergic to those type of questions."
Other actors attending included Mike Myers, who plays the lovable green ogre Shrek, Antonio Banderas and Rupert Everett.
"Shrek the Third" opens nationwide in Britain on June 29.
The discovery of the submarine has unveiled a few "inconsistencies." For example, how can one explain the fact that the sub was found where it needed to be searched for from the start?
When on a state visit to Singapore, Russian President Vladimir Putin promised to revisit the discussion of the 1956 Declaration between the USSR and Japan regarding the issue of the peace treaty with Japan
The TurkStream, which runs along the bottom of the Black Sea from Russia's Anapa to Turkey, will consist of two lines, each with a capacity of 15.75 billion cubic meters of gas a year