Jude Law said he had never known that anyone in his family had been paid for information but had become aware recently that someone had been approached by the News of the World.
He also accepted that his publicist had frequently talked to reporters at the newspaper but could not be specific about this story.
"There were so many stories," he said, adding: "I seemed to have a publicist on speed dial so I could keep up with what was being written."
The names of the relative, the publicist and a former employee who it was suggested had also given information, were not revealed in court.
Instead, two pieces of folded paper with the names on were handed to Mr Law.
He acknowledged the names, which the court was told were being withheld because of the need to protect the identity of sources.
Andy Coulson was told about a recording of a voicemail from actress Sienna Miller on actor Daniel Craig's phone, his trial has heard.
Jude Law discovered for the first time today that a relative had allegedly been paid by a newspaper for information.
A former tabloid reporter has revealed to the phone-hacking trial how the "dark arts" were used by newspapers to secure stories.