He was chased briefly by a security staff member and a patron.
While running through the park the man dropped items related to the robbery, including some cash.
A scene examination and witness statements were underway, police said.
Victim support has been offered to those who were present at the time.
Tavern Harewood's general manager said staff and customers present at the time were safe and that he would not be making any further comment about the incident.
This was the second armed incident at the Tavern this year.
In January a man entered the Tavern with a sawn-off shot gun and stole money.
No one was injured but the two managers working at the time had found the event traumatising, Detective Andrew Owens said in January.
Eleven police cars responded to the tavern, including a dog unit, however the man was not located.
A staff member at a neighbouring Hell pizza on Harewood road, who asked not to be named, said crime in the area had been rife recently.
"[There's been] a massive influx - we've been broken into a few times, the dairy down the road got robbed. That was just a few weeks ago."
On Valentines day this year two people were stabbed during an aggravated robbery at the Harewood Rd Dominoes pizza shop.
Two disguised men entered the store carrying a firearm and a knife and threatened two staff members. Despite following the requests of the offenders, both were stabbed.
One received serious but non-life-threatening wounds to the stomach and was taken to Christchurch Hospital, the other was treated at the scene.
Staff working at Hell last night had noticed police in the area after last night's robbery, but had not seen anything else to do with the incident.
Christchurch CIB would like to hear from the public about any suspicious activity around the Bishopdale Tavern.
If anyone found items such as cash, or clothing in Bishopdale Park, or the surrounding area they were asked to contact police.
Police also urge that members of the public report any suspicious behaviour around their local shops and bars to assist in preventing further occurrences of this nature.
Urgent calls can be made to 111 and other information can be passed on anonymously via the CrimeStoppers Line 0800 555 111.
