In a lengthy release posted on the NPR Web site, Edwards made no mention of why the job was open. Knell fills the vacancy created when Vivian Schiller quit in March following the revelation of derogatory comments made by NPR's former senior vice president for fund-raising made about Tea Party members that were captured on a hidden camera by a Republican activist.
Ron Schiller (no relation) had called Tea Party members xenophobic and "seriously racist." He also departed NPR.
Joyce Slocum, NPR's senior vice president of legal affairs and general counsel, has been serving as interim CEO.
Vivian Schiller became chief digital officer of NBC News this summer.
Knell has been CEO of Sesame Workshop for more than a decade.
"Gary is an extraordinary leader with extensive experience in public media, programming and education," Edwards said. "He has the skills, experience, talent and vision to lead NPR into an even more dynamic future, while maintaining its commitment to serve Member stations and the public,"
Knell said he was "thrilled" to be taking over at NPR.
"Over the past 40 years, it's grown from an inspired idea to one of the world's most respected and leading providers of news, music and cultural programming -- both on the air and across ever-expanding digital platforms," Knell said. "This is media with a deeply held mission, compelling history and boundless future. Simply put: it's journalism at its best. What an opportunity to work with the incredibly talented staff here, and to partner with stations, as we continue to innovate, expand civil dialogue and set the standard for media."