New Orleans Saints' Coach Sean Payton made the announcement at a press conference after Saturday's Rookie Camp practice and surprised Walker, who had come from graduation ceremonies at Tulane University, where he studied cell and molecular biology.
Walker suffered a spinal injury on Sept. 8, 2012 – leaving him paralyzed from the neck down – when he collided with another player while playing safety for Tulane.
"When Devon got hurt, his football career was just starting to take off after three years of hard work," Payton said on the New Orleans Saints website.
"Despite the devastating injury he suffered, Devon refuses to let that define him. He is an outstanding young man, who is not only an inspiration to his coaches and teammates at Tulane, but to all of us. Devon's character, determination, intelligence and work ethic are everything that we look for in a New Orleans Saint when we sign a player."
Walker said getting a contract from the Saints was "like one of my dreams come true," reported the Associated Press.
"I've been a Saints fan almost since I was walking as a child," said Walker, who grew up in the New Orleans suburb of Destrehan. "Just to be a part of the team and be around the players is more than I could hope for."
At the press conference, Payton said he was proud of Walker's recovery.
"All of [the players] became better for having been around Devon and the inspiration he's given," Payton said at the conference. "It rubs off. We're excited to have him."