Ronning, 36, led the Predators in most major offensive categories with 18 goals and 31 assists while playing all 67 games. He will provide depth up the middle for the Kings, who have been one of the hottest teams since the Olympic break and already boast centers Jason Allison and Bryan Smolinski.
"I haven't seen him play much over the years, he's always been in the other conference," Allison said. "But I have seen him score goals against us and he's had some great stats over the years. He puts the puck in the net."
Last week, the 5-8 Ronning became the 176th player in NHL history to appear in 1,000 games.
"He's a good power-play player, he's very good on the half-wall," Kings coach Andy Murray said. "He'll certainly play an offensive role for us. That is the kind of player he is."
The trade was the second in four days for the slumping Predators, who have all but abandoned the race for the first postseason berth in team history.
"This move will improve our defense considerably and allow some of our younger forwards like Denis Arkhipov, David Legwand and Petr Tenkrat to shoulder more of the offensive load," Nashville general manager David Poile said.
"Cliff Ronning has been our top offensive player in this franchise's first four seasons. He has given us four great years. This trade gives Cliff an opportunity to go into the playoffs with one of the league's hottest teams."
On Tuesday, the Predators traded right wing Tom Fitzgerald, the only captain in team history, to Chicago for a draft pick. Nashville has lost three straight, is winless in its last five games and trails Dallas by 13 points for the final Western Conference playoff spot.
Karalahti battled drug problems over a two-year period and was convicted six years ago in his native Finland before receiving a three-month suspended sentence.