Rupp, 31, played the past two seasons with the Pittsburgh Penguins, and scored nine goals and added eight assists in 81 games last year for Pittsburgh. In 2009-10 with Pittsburgh, he had career highs in goals, points, shots on goal, plus-minus and hits.
"This is an awesome moment for me & my family," Rupp said via the team's Twitter page. "It will be an honor to be a member of the Blueshirts."
Rupp's deal is for three years and $4.5 million, according to The Associated Press.
The 6-foot-5, 230-pound center has also played with the New Jersey Devils, Columbus Blue Jackets and Phoenix Coyotes in his career and has scored 49 goals and tallied 40 assists while accumulating 656 penalty minutes in 497 games. Rupp has played in 43 playoff games, winning the Stanley Cup in 2003 with the Devils, and has scored two goals.
The Islanders originally drafted Rupp, a native of Cleveland, in the first round in the 1998 draft, but he would re-enter the draft in 2000 and the Devils selected him in the third round with the 76th pick. He scored the first hat trick of his career on Nov. 30, 2009, at Madison Square Garden.
Rangers backup goalie Martin Biron called it "a great signing."
"He's going to bring a lot of size and he's big forward," Biron said. "He's very smart getting to the front of the net with his size and it's hard to move him around and he can contribute in any aspect of the game. He's a pretty tough guy and can talk with his fists but he's a force who can play the power play and every situation. With what the Rangers are trying to put together as a club, his addition is going to help toward that identity."
While the Rangers did sign Rupp, they still remain in the hunt for top free-agent center Brad Richards to try to help their offense. The Los Angeles Kings, Toronto Maple Leafs, Buffalo Sabres and Tampa Bay Lightning are other teams who are highly interested in Richards.
The Rangers also re-signed forward Ruslan Fedotenko Friday night to a one-year, $1.4 million deal.
Fedotenko made the team on a training camp tryout last season and played 66 games, contributing 10 goals and 15 assists. The 10-year veteran has scored 160 goals and notched 173 assists in 743 games, which also includes previous stops in Pittsburgh, Tampa Bay, Philadelphia and with the Islanders.
Matt Ehalt is a regular contributor to ESPNNewYork.com.