The 13-episode first season is to premiere on the video-streaming service in 2015.
A veteran of the Hunger Games and Mighty Ducks film franchises, Henson will play Foggy Nelson, Matt Murdock's best friend and legal partner, in the small-screen adaptation of the Daredevil comic books.
Charlie Cox is playing Matt/Daredevil on the show, which will also feature Vincent D'Onofrio and Rosario Dawson.
"Elden plays one of the most important characters in the world of Marvel's Daredevil, and we're thrilled to see Foggy Nelson brought to life by such an incredibly talented actor," Jeph Loeb, Marvel's head of television, said in a statement. "He perfectly captures the heart and soul of this series, bringing an added resonance to Matt Murdock's fight against the injustice in their great city."
Marvel's Daredevil follows the journey of Matt Murdock, who was blinded as a young boy but imbued with extraordinary senses. As an adult, he fights injustice by day as a lawyer and by night as the superhero Daredevil in modern-day New York City.