The 34-year-old defenseman signed a seven-year contract extension with the Toronto Maple Leafs on Dec. 31, 2013.
Phaneuf had six points (one goal, five assists) in 67 games with the Kings this season, and 16 points (four goals, 12 assists) in 93 games over the past two seasons.
He was acquired by Los Angeles with center Nate Thompson in a trade with the Ottawa Senators for forward Marian Gaborik and center Nick Shore on Feb. 13, 2018.
Selected by the Calgary Flames with the No. 9 pick in the 2003 NHL Draft, Phaneuf has 494 points (137 goals, 357 assists) in 1,048 regular-season games with the Flames, Toronto Maple Leafs, Senators and Kings. He has 21 points (seven goals, 14 assists) in 55 Stanley Cup Playoff games.