Until 24 January 2010, Mersiades was Head of Corporate and Public Affairs with the Football Federation Australia and was also a member of the Senior Management Team for the Australian 2018 and 2022 FIFA World Cup bid.
Mersiades became co-founder of an advocacy group campaigning for independent reform of FIFA, #NewFIFANow along with British MP, Damian Collins, and Australian-Swiss businessman, Jaimie Fuller.
#NewFIFANow held their first forum at the European Parliament in Brussels[8] in January 2015, in where Mersiades spoke along with Harold Mayne-Nicholls and Lord David Triesman.
[10] Mersiades later worked as National Public Affairs Manager for the Australian Red Cross Blood Service.
[16] In 2018, Mersiades published a book titled "Whatever It Takes: The Inside Story of the FIFA Way", an investigative piece detailing the bidding process into the awarding of the 2018 and 2022 FIFA World Cups to Russia and Qatar respectively, and what ultimately led to Australia's failed World Cup bid.