A balaclava-clad man pulled his victim to the floor during an attempted robbery in the Great Oakley area of Corby.
Police are appealing for information about the incident which took place at about 11.40pm on Saturday, April 20.
A police spokesman said: “The victim, a 56-year-old man, was walking along Conyger Close when he was approached from behind and pulled to the floor.
“The offender asked the victim to hand over his phone.
“The victim said he didn’t have one, so the offender ran off empty-handed towards Lewin Road.”
The offender was a white man, in his early twenties, approximately 5ft 11in and of a stocky build.
He wore a dark coloured tracksuit top with the zip up, dark coloured tracksuit trousers with two white stripes down the legs, dark shoes and a balaclava over his face.
The victim had noticed the man running past him a few seconds before the incident happened and saw he had dark cropped hair.
Police would like to speak with a man who was walking in the area at the time, as well as the occupants of a vehicle, who stopped and spoke with the victim after the incident occurred.
Witnesses to this incident, or anyone with information about it, can call Northamptonshire Police on 101 or information can be given anonymously to Crimestoppers on 0800 555111.