The video released on Monday is the latest public plea from the Today show host about 84-year-old Nancy Guthrie since her disappearance on February 1 from her home just outside Tucson, Arizona.
Savannah Guthrie said her family will never stop looking for her.
"The world can be a cruel and unforgiving place, and I know that you have tried to do things the right way," she said. "So I'm asking you, begging you, to do the right thing now. Make the right choice. Help us find her. Tell us where to look for her. I truly believe it is never too late to do the right thing."
Authorities believe Nancy Guthrie was kidnapped, abducted or otherwise taken against her will on February 1. They found blood near the front doorstep of her home just outside Tucson, and the FBI later released surveillance videos showing a masked man on the porch that night.
A volunteer group recently searched for her body near the Arizona-Mexico border. Authorities have not said how many purported ransom demands were made after Guthrie's disappearance, though three news organisations reported receiving such notes and turned them over to investigators.
The FBI has discounted some of the ransom notes as nothing more than extortion attempts, but said it's still evaluating others that might be legitimate.
In the days after the disappearance, Savannah Guthrie and her siblings acknowledged they were aware of media reports of a supposed ransom letter but wanted proof their mother was alive. Weeks later, she said her family was offering a $US1 million reward for information leading to the recovery of her mother.
