Senior Sergeant Anthony Bond, of Dunedin, said the fight broke out around 12.40pm yesterday.
A 32-year-old man had been walking in the area when his uncle, a 53-year-old man, spotted him.
The two relatives became embroiled in an argument that turned to pushing and shoving.
The altercation escalated and the uncle allegedly kneed and punched his nephew in the head.
Police arrested the uncle and charged him with assault.
He would appear in Dunedin District Court at a later date.