Horn, who had dementia, walked with a limp and was non-verbal, had gone missing from a suburban Richmond rest-home.
Detective Alun Griffiths, of the Invercargill police, said the body was found among trees near Bill Richardson Dr, in an industrial area.
He said formal identification was yet to take place, and police would not be in a position to comment further on the circumstances of the death until after a postmortem was completed.
Wayne Horn, who lives in Christchurch, said the family was notified about 1.30pm yesterday.
He had not given up on his brother.
"Because of the length of time, I had to think of the outcome, but we just wanted him home one way or another. And we've got him now."
Even though they were waiting on confirmation the body belonged to his brother, they knew it was him, he said.
He said his brother would be home soon.
Describing his brother as "bloody awesome", the impact he had on those who knew him became obvious.
"He lived in Ashburton before he moved to Christchurch, and the posters I put up were in the areas he lived in.
"A lot of people broke down into tears when I gave them the posters I put up. They couldn't believe it."
His brother enjoyed taking morning walks.
"On Monday, he did his usual thing. But he never returned."
Wayne said they expected DNA confirmation from the coroner today.
"Then we'll all get together."
The area where the body was found was near the Waihopai River, which had previously been searched by police.
The search had focused intensely on Queens Park, as Horn was captured on CCTV footage walking there on the morning he went missing.
