The decision to terminate Halperin's contract makes permanent a preliminary announcement last week from NBC saying he would not appear on NBC pending a review of the allegations.
A dozen women have accused Halperin of unwanted contact, including assault, while he was political director at ABC News over a period stretching from 1994 to 2004.
NBC is the last of Halperin's several employers to drop him since CNN broke the news of his alleged misconduct Wednesday night.
HBO said last week it was dropping a miniseries based on "Game Change," the bestselling book series about presidential campaigns that Halperin co-authored.