The deal will keep Carney on the stage in "Spider-Man: Turn off the Dark" through May rather than November as his original deal specified.
"I am thrilled to be on stage nightly as Peter Parker and Spider-Man," Carney said in a written statement. "I can't imagine a more wonderful, harder-working company than my mates on Broadway."
The new pact includes a provision that will allow Carney to take some time off in the winter to star in a movie about musician Jeff Buckley. Matthew James Thomas and Matt Caplan will fill in as the super hero.
Britain's The Daily Telegraph said Carney's new deal indicated the producers were more confident the high-priced musical would make it through the winter doldrums, which are typically much slower at the box office.
"Spider-Man" labored through a high-profile series of on-stage accidents and scathing reviews but has opened to a positive reception from the public. The New York Time said tickets sold briskly this summer and the show took in $1.7 million.