Gaspin's decision, announced in a memo to NBC employees, follows NBC Universal chief Jeff Zucker's September announcement that he would leave after cable provider Comcast takes over the media giant.
Possible executive changes have loomed since last December, when Comcast agreed to buy a 51 percent stake in NBC Universal from General Electric Co. The merger still is undergoing regulatory scrutiny but could be concluded by the end of the year.
Comcast chief Steve Burke has "determined that he wants to move in a different direction and given the scope of my current responsibilities, we could not agree on an appropriate role for me in the new company," Gaspin said in the memo. NBC provided the memo Monday upon request and without comment.
Burke, who is set to replace Zucker, reportedly has settled on a new executive team for NBC Universal that will include former Showtime programming head Bob Greenblatt, who will oversee entertainment programming at ratings-challenged NBC.
Greenblatt stepped down from Showtime this summer at the end of his contract and is known for bringing it such hit shows as "Weeds" and "Dexter."
NBC, which finished last year in fourth place in the ratings and has struggled in the new season, announced a shakeup of its schedule for midseason.
Gaspin was named chairman in summer 2009 after overseeing the company's stable of entertainment cable networks such as USA, Bravo, SyFy and Oxygen. In his memo, he noted his involvement in the success of NBC Universal's cable assets and strides made in digital innovation.
Comcast, the nation's largest TV signal provider serving some 23 million subscribers, said in December it would buy a 51 percent stake in NBC Universal from General Electric for $6.5 billion in cash plus cable channels it owns such as E! and Style valued at $7.25 billion.
Federal regulators are examining the deal for antitrust concerns given the huge presence the combined entity would have in the creation and distribution of entertainment programs over the airwaves and online.
