Williams replaces Scott Perry, who recently departed to join the New York Knicks as their new GM.
"I'm excited about this," Williams told The Undefeated. "It's really attractive to be part of a start up. That's the way that Vivek [Ranadive, owner] sees the Kings. He's a couple of years into ownership. He's forward thinking."
Terms were not disclosed.
"We are so excited that Brandon is joining our front office team," said general manager Vlade Divac. "He is an experienced and talented basketball executive. His knowledge of player development and basketball operations combined with his legal skills will be a strong addition to our team."
In a press release, Williams will deal with the day-to-day operation, including roster composition, player evaluation and development and contract negotiations.