Avery had 10 goals, 18 assists and 116 penalty minutes in 55 games this season with the Kings, who also acquired the rights to unsigned forwards Marc-Andre Cliche and Jan Marek. Los Angeles sent 19-year-old prospect John Seymour to the Rangers.
"Some teams were actively pursuing Sean, the New York Rangers were very aggressive," Kings general manager Dean Lombardi said. "From our standpoint, the key is the young player, Cliche, who has impressed us."
Avery has made more of a splash off the ice.
The brash left winger received a league reprimand in September 2005 when he made derogatory comments about French-Canadian players after then-Phoenix defenceman Denis Gauthier hit former Kings teammate Jeremy Roenick in an exhibition game. Avery issued an apology.
He also was outspoken a few months later when he received a fine for diving during a game. Avery complained about the punishment, which resulted from a second offense, and drew a second US$1,000 fine. He suggested that the NHL singled him out because of his earlier comments.
As part of his protest to the diving fine, Avery chastised union members on the league's competition committee - including new Rangers teammate Brendan Shanahan - for agreeing to such penalties that aren't subject to appeal in the collective bargaining agreement.
The 26-year old Avery had 257 penalty minutes in 75 games last season along with career highs of 15 goals, 24 assists and 39 points. He signed a one-year contract with the Kings before this season worth $1.1 million and can become a restricted free agent in the summer.
"He's been good," Lombardi said. "All year he's learned to be a better teammate. He comes to play every night. Sometimes emotion gets the best of him. I think he's made marked improvement this year.
"Sometimes players just take a little time to mature. Sean's still young, hopefully he'll continue to do so. He's going to a big stage now. If he continues (to mature), he'll do just fine. From the summer, when I first got there, there wasn't much of a market for Sean Avery. He's made progress."
The deal was completed shortly before the Rangers faced the Detroit Red Wings, Avery's first NHL team. He is expected to join the team for Tuesday's game at New Jersey.
New York has been looking for a spark while trying to break out of a slump in which the Rangers lost six of nine and 13 of 20. They were held to two goals or fewer 11 times during the stretch that dropped them below the cutoff line in the Eastern Conference playoff race.
Ward, who can be an unrestricted free agent after the season, had four goals and six assists in 46 games. He was scratched for five of New York's previous seven games.
Seymour had one goal and five assists in 34 games with the Brampton of the Ontario Hockey League.
The Kings, last in the Western Conference, are looking more to the future.
Cliche, 19, has 15 goals and 21 assists in 35 games with Lewiston of the Quebec Major Junior Hockey League, while Marek posted 17 goals and 26 assists in 42 games with Magnitogorsk of the Russian Hockey League.
"Jason Ward obviously is an NHL player, he can come in and play for us right now," Lombardi said. "A player like Cliche, who played for the Canadian National team, this kid works his tail off, he's the type character we're looking for.
"Marek is one of the leading scorers in that league. He's got a lot of skill and is made for this game. Two players who have some upside and a player (Ward) who can come in and play now. I think this made a lot of sense for us."