Ticketek Australia says the names of some of its customers, as well as their dates of birth and email addresses, may have been accessed in a significant data breach.
It comes just days after rival company Ticketmaster was reportedly attacked by a hacker group, which stole customer information.
In that case, a hacker claimed to have stolen the data of 500 million people from Ticketmaster.
Meanwhile, Ticketek said the information accessed was stored in a cloud-based platform hosted by what it described as a "reputable, global third-party supplier".
No customer passwords or payment details had been compromised as it had secure encryption methods and a separate system to process online payments, it said in a statement.
Ticketek was now notifying customers who may have been impacted, and was working with Australia's National Office of Cyber Security.
It apologised for any concern the news may cause and recommended that its customers remain vigilant for potential phishing emails and other scam communications, including from organisations purporting to be from Ticketek.