The man, known only as Sanjay, walked in on his partner and a next-door neighbour in their Mumbai home.
And when she refused to apologise he climbed a nearby guava tree and has been there ever since.
The 25-year-old has survived on a diet of fruit from the tree and food handed up by relatives.
“He eats and sleeps on the tree and even relieves himself from there,” his sister told The Asian Age newspaper.
Police have said they can’t intervene because he hasn’t committed an offence.
A spokesman for Cholapur police confirmed: “The man is on a tree top for the last nine months over some domestic dispute.”
Sanjay’s wife has since returned to live with her parents – and has still not said sorry.