The 36-year old Arnott is one of many Devils who have struggled this season. The Collingwood, Ontario native has 13 goals and 11 assists in 62 games.
Arnott should bring extensive playoff experience to the Capitals, as he helped the Devils capture the Stanley Cup in 2000.
"I'm at the end of my career," Arnott said. "I want a chance at another Stanley Cup.
"I think Washington has a good potential to be a Stanley Cup championship team."
A veteran of 16 NHL seasons, Arnott has accumulated 396 goals and 501 assists in 1,161 games split between the Devils, Dallas Stars, Edmonton Oilers and Nashville Predators.
Arnott was originally selected seventh overall by the Oilers in the 1993 NHL Entry Draft. He is earning $4.5 million this season and is scheduled to become an unrestricted free agent on July 1
The 28-year-old Steckel has five goals and six assists in 57 games this season. He has two seasons left on his contract.
"He can be used in all situations," Devils general manager Lou Lamoriello said, "especially when the game is on the line."