The Rangers made the move Friday, during the first day of the NHL's free-agent signing period, while waiting to hear if they would land coveted center Brad Richards, who highlighted this year's class of unrestricted players.
Later Friday, the Rangers re-signed 32-year-old forward Ruslan Fedotenko for one year, $1.4 million. Fedotenko had 10 goals and 15 assists in 66 games last season with New York.
The 31-year-old Rupp, who scored the Stanley Cup-winning goal for New Jersey in 2003 during Game 7 against Anaheim, had nine goals, eight assists and 124 penalty minutes in 81 games last season with Pittsburgh.
In 497 NHL games with New Jersey, Phoenix, Columbus and Pittsburgh, Rupp has 49 goals, 89 points, and 656 penalty minutes. He has surpassed 100 hits in each of the last five seasons.