Sezer was born in Bankstown, New South Wales, Australia to a Turkish father, Yücel, and Indigenous Australian mother, Tanya, and is Muslim.

Sezer played his junior football for the East Hills Bulldogs before being signed by the Canterbury-Bankstown Bulldogs. Sezer played in the Bulldogs Toyota Cup team in 2010-2011, scoring over 300 points. On 31 August 2010, Sezer was named at five-eighth in the 2010 NYC Team of the Year. At the end of 2011, Sezer signed with the Gold Coast Titansafter a lack of first-grade opportunities at the Bulldogs.