The incident happened near Redwell School at about 10pm on Friday, October 13, while the victim was walking his dog.
A spokesman for Northants Police said: “A man grabbed him around the neck and demanded he hand over his wallet and phone.
“He told them he didn’t have anything to give and the offender patted him down to check before pushing him away.
“The victim turned around and saw two men running away towards Harrowden Road.”
One of the suspects is described as black, about 6ft, with a medium build and in his mid to late 20s.
He wore black jogging bottoms, a dark-coloured hooded top, Nike trainers and ran with a limp.
The second man is described as about 5ft 11in and with a skinny build.
He wore a black hooded top, jogging bottoms and white trainers.
Any witnesses to the incident are asked to contact Northamptonshire Police on 101 or Crimestoppers anonymously on 0800 555111.