Spike Quinn was digging soil around the foundations of his home when his fork unearthed an unusual item.
"It just fell out on to the rest of the soil ... and I thought that looks like a mortar round."
He moved it to his garden and buried it under some compost, before contacting police.
Police took photos of the item, speculating it may be a World War 2 vintage reusable practice round.
"I am not allowed to keep it unfortunately."
Mr Quinn rejected a suggestion his discovery was an attempt to get out of his DIY jobs.
Acting Senior Sergeant Dave Scott, of Dunedin, confirmed the New Zealand Army bomb squad examined the photo and believed the item to be the "nose of an expended practice round", and was unlikely to explode.
The bomb squad was due to arrive in Dunedin from Christchurch today to dispose of the item
