Halderman, an Emmy Award-winning producer at CBS News, is accused of threatening to reveal the married talk-show host's sexual relationships with female staffers if Letterman didn't pay him $2 million.
Instead of paying him, Letterman turned him into the authorities and admitted his misdeeds on "Late Show with David Letterman."
ABC News said the plea deal Halderman agreed to Tuesday requires him to serve six months in prison and perform 1,000 hours of community service. He also will be on probation four and a half years.
Halderman initially pleaded innocent to charges of grand larceny and could have faced a 15-year prison sentence if convicted, ABC News said.
He is due to be sentenced May 4.