The plea for public assistance comes after a 19-year-old man was robbed at knifepoint while he walked home from the Ballarat Railway Station on Monday, January 19.

The victim was walking to a friend's house in Walker Street via Lydiard Street North at 11.40pm.

Ballarat Police Crime Investigation Unit Detective Sergeant Steve Howard said the victim was approached on Walker Street at 11.40pm, 100 metres from the intersection with Lydiard Street North, by two males.

Detective Sergeant Howard said an 18-year-old man produced a knife and demanded the victim's mobile phone and wallet which he handed over.

The victim fled the scene shortly after this incident in which no one was injured.

The males are not believed to have followed the victim from the train station.

The man with the knife is described as wearing a green peaked cap, grey hooded jumper and blue jeans. 

The other man police wish to speak to is described as about 15-years-old, light brown hair and wearing a blue silky jumper. 

Any witnesses who may have knowledge of the incident or knowledge of offenders are urged to contact Crime Stoppers on 1800 333 000 or Ballarat Police Station on 5336 6000.