Dunedin police released a picture of the black-handled hunting knife, which was found by a member of the public on a soccer ground at Chingford Park yesterday.
Detective Sergeant Dave Nelson said the knife might have been used in the aggravated robbery at the Northeast Valley pub on Monday night.
Police are also seeking information about a man seen hanging around the tavern last week, and who may have been involved in the robbery.
The publican, who was locking the premises about 8pm, was robbed at knife-point and received a small cut to his chin.
The incident took place in the dark car park at the rear of the building. The publican told the Otago Daily Times the incident was "all over fairly quickly".
"When he took off, I locked the door, rang 111 and the police were around here very fast."
He did not realise the knife had nicked his chin until the police pointed out he was bleeding, he said.
The man, described as being about 177cm tall, wearing dark clothing and face coverings, demanded the publican's bag of cash as well as money from his wallet.
Police would not disclose the amount of money stolen.
Det Sgt Nelson said "of interest, a male has been seen hanging around the area last week for a couple of nights".
"We are interested in hearing about anyone acting suspiciously around the tavern over the past week," he said.
About eight officers are investigating the incident.
Det Sgt Nelson could not rule out a connection to the aggravated robbery of Forbury Pharmacy by a knife-wielding man last Wednesday, in which prescription drugs were stolen.
Such incidents were not common in Dunedin, he said.
Anyone with information can call Dunedin police on (03) 471-4800 or Crimestoppers anonymously on 0800 555-111.
