Local pub Evs Bar said the man had been in more than a week ago, and they had given the premises a deep clean.
"It has come to our attention that the confirmed case of Covid-19 in Carterton is also a frequent patron at our bar. In saying that, we have established he was last present about 8 days ago," said a post on the bar's Facebook page on Saturday.
They were currently open with a 50-person limit, and "strict social distancing" would be enforced.
"Please know that we are doing everything we can to ensure this is a safe environment for everyone, so please help us by maintaining good hygiene practices, wash your hands regularly, and limit close contact."
Another post said staff spent "hours and hours" scrubbing every surface of the pub to make sure it was clean.
"Our bar, along with all the others, may not be open for much longer. So visit while you can, enjoy a quiet beer and a catch up with friends, and be assured we are doing everything we can to make it a safe and enjoyable environment."
Lang said businesses around Carterton were currently coping, and that the community was caring and resilient.