Mesopotamia in York Place, Brighton, was caught selling to under-18s on three occasions in a test-purchase operation mounted by police and Trading Standards.
Hasan Sengoz had his licence suspended for three months. Another store in the city, Three to Four in Western Road, was also caught selling to minors and faces a six-week licence suspension.
Councillor Denise Cobb, chairman of Brighton & Hoveís licensing committee, said: "This licensing authority considers the selling of alcohol to children as extremely serious and those who consistently flout the laws are likely to end up losing their licence.
"When these two premises come back into operation there will be extra conditions to make sure staff are trained in what to do when young people attempt to buy alcohol."
Councillor Jeane Lepper told the Argus newspaper that the issue at Mesopotamia was "difficult".
She added: "We don't want to stop the business from being able to trade, but if they are serving under-age drinkers because they cannot communicate with them then we must do something."