Daniel Morgan, 24, had his arm broken in three places after being attacked by Andrew Chamberlain, a court heard.
Chamberlain hit Mr Morgan with the 4ft metal pole after the neighbour left his car outside Chamberlain's home in Greenfield Terrace, Blackwood.
The 50-year-old, who was convicted of grievous bodily harm with intent at Cardiff Crown Court, said he used the pole in self defence.
The court heard parking was a "contentious issue" on the street and residents agreed to only park outside their own homes.
When Mr Morgan parked outside Chamberlain's home, he became "abusive and threatening," the court heard.
He took the large metal pole from his garden and Mr Morgan said he blocked a blow with his arm.
He said: "It was excruciating pain as I am sure you can imagine."
Chamberlain told the jury: "When I lifted the pole up he punched out at me with his left hand.
"As I was bringing the pole down, it made contact with the side of his arm."
Mr Morgan said he was not aware of any parking restrictions.
Sentencing was adjourned for reports to be prepared and Chamberlain was released on bail but Recorder Peter Griffiths QC warned him he faces jail.
A man attacked his neighbour with a scaffolding pole in a parking row.