The largest truffle ever grown in Australia, worth about $2,000 per kilo, has been unearthed in the New South Wales Southern Highlands.

The 1.172 kilogram French black perigord fungus falls just short of other large truffle finds made overseas.

Some of the largest truffles found include a white truffle weighing 1.31kg found in Croatia in 1999 and a 1.3kg truffle found in the south of France and sold in 2012.

Truffle producer Ted Smith said he usually used his dog to sniff out the delicacy, but he spotted this one sticking out of the soil at his farm in Robertson.

He said he realised the fungus was big when it set off an alarm on his scales, prompting a trip to the post office to use their bigger scale for a reading.

"It felt quite weighty," he said.

The fungus was dug up at a truffle farm at Robertson, in the NSW Southern Highlands. ( Supplied )

"I knew it was big but it was only when I got back to the homestead here, washed it, cleaned it, dried it and weighed it, it went off the Richter on the measuring device that I had and set off an alarm."

The truffle has been sold to a local winery and restaurant for an undisclosed amount.

While Mr Smith is hopeful he can grow another one, actually doing so is a mystery.

"I wish we knew that, I think a lot of other people would like to know that too," he said.

"All I can say is I think we're in God's own country up here at Robertson in the Southern Highlands of New South Wales.

"The soil is rich red soil where we are; we have what we think are the ideal conditions that compare with central France and Northern Italy."