At least 60 people who turned up to ZZ Top and Brian Wilson concerts in the city last week had bought invalid tickets.
Aiken Promotions says the tickets were purchased on secondary sites and the disappointed fans had to be turned away from the venues as a result.
The music promoter has issued a stark warning to fans against purchasing tickets from secondary websites.
"Unfortunately it is NOT likely these people will get the money they paid refunded" said Peter Aiken.
"As a promoter, it is extremely frustrating to see people being exploited like this and I would like to emphasise once again that fans should not purchase tickets from any secondary sellers."
Brian Wilson performed at the Bord Gais Energy Theatre last Tuesday while ZZ Top played to the crowds in 3Arena last Friday.