During the proceeding, the 41-year-old actor revealed he had an angry phone call with the James Bond star in 2005 after finding out that his then-fiancée had cheated on him with his then-friend.
"We had known each other many, many years," Law recalled. "So the conversation took on all sorts of turns."
At the time, Craig was in a relationship with actress Satsuki Mitchell. Law reportedly told the court he encouraged Craig to fess up to her about the affair during the call.
News of Miller's affair with Craig broke in October 2005 when News of the World (NoW) published a story with the headline “Sienna cheats on Jude” after the twosome starred together in the 2004 movie Layer Cake.
Since then, Craig went on to marry his Dream House costar Rachel Weisz and Miller tied the knot to actor Tom Sturridge, both in 2011. Law, who was married to Sadie Frost from 1997 until 2003, is currently single.
The Academy Award-nominated actor appeared in court Monday to give his testimony against NoW for violation of his privacy.
Former NoW editors Rebekah Brooks, 44, and Coulson, 44, are accused of conspiracy to intercept voicemail communications, along with ex-NoW news editor Ian Edmondson and managing editor Stuart Kuttner, between 2000 and 2006.