Cornwall's largest beer producer, St Austell Brewery, has banned all customers from smoking e-cigarettes in its premises.
Managing Director James Staughton said the ban will cover all 25 pubs the brewery manages, and will take effect immediately.
He said he had imposed the ban because of uncertainty over whether the use of e-cigarettes can be harmful to people's health.
The news comes after a report published by Social Change UK which highlights that youngsters are starting to use e-cigarettes as an alternative to smoking.
The group claims they are now available in more than 300 different flavours, including gummy bear and Red Bull.
Kelly Evans of Social Change UK said there is a UK-wide and European problem - with children as young as 11 and 12 using them in parts of Wales.
She said that although there is no research to suggest they are harmful, it would be beneficial to see some regulation.