The masked robber had pulled out a knife in a supermarket in Sussex, but left empty-handed after being hit by the loaf and some bottles of squash.
Officers praised the pair's bravery, but said they still need to track down the suspect.
Sussex Police said a man walked into an Express Supermarket in Worthing just before 10pm on Monday and demanded that staff empty the till.
But he got more than he bargained for when the girl and her father, who had been shopping at the time, spotted him and took action.
In a dramatic encounter captured on the shop's CCTV, the pair threw two bottles of squash and a loaf of bread at him and, after one last unsuccessful attempt to grab money from the till, the raider fled empty-handed out of the shop.
No-one was harmed, police confirmed.
Detective Constable Noel Simmonds said: "I cannot praise enough the bravery of the father and daughter who intervened in this knifepoint attempted robbery.
"There are considerable risks any time a knife is used or brandished, and whilst it is tempting to just view the spectacle of an armed robber fleeing in panic from a young girl, if the suspect is not caught he may try again, and next time someone could be seriously hurt.
"We need to identify the suspect as quickly as possible so we are asking people to view the CCTV footage and stills and to please get in touch with us if you know who did this is or have any information about the incident."
The suspect is white, slim, about 5ft 8in and was wearing a green Nike hooded jacket with the hood up, a black baseball cap, blue jeans and green Adidas POD trainers, police said.
He had a scarf covering his face and was also wearing gloves.