The company says Gardaí are investigating an individual based in the capital.
Ticketmaster is urging locals looking to attend concerts, matches or other events to be extra vigilant for fraudulent sellers.
The company says Gardaí are investigating an individual based in Dublin.
Ticketmaster says some people have already lost what its called "large sums" of money to this individual, who is claiming to represent it.
It says this fake seller is promising advance tickets or last minute tickets for collection from the venue on the day of the event.
These tickets don't exist.
Ticketmaster is working alongside Gardaí to boost its security and verification methods for upcoming events.
It's also urging anyone who has been a victim of this crime to get in touch with Gardaí immediately.
The company's statement is co-signed by partners including Croke Park, Landsdowne Road, the FAI, IRFU, MCD and the company that organises Electric Picnic.

Spain To Launch €60 Unlimited Travel Pass As Irish Campaigner Calls For Better Service Frequency
Fines And Jail Terms Proposed For Sellers As Crackdown On Disposable Vapes Begins
Lower Childcare Fees Promised - But Providers Say They Are Being Ignored
Man Accused Of Assaulting 10-Year-Old In Saggart Tells Gardaí Child Said "She Was 18"
Up to 100 Maynooth Students Face School Travel Chaos After Bus Service Pulled
Children Eating At Desks And Walking On Public Roads As Curragh Community College "Bursting At Seams"
Four Kildare Schools Included In New Round Of Safe Routes To School Programme
Three Motorists Fined During Naas School Run As Children Were Not Wearing Seatbelts