Sydney Olympic FC
Triantis' youth career began in 2009 at APIA Leichhardt Tigers before moving a year later to Sydney Olympic FC where he quickly forced his way into the First Grade squad. After amassing 49 games for Olympic and winning a title with them in the process, Peter was brought into the Sydney FC youth setup in 2012 under Brian Dene and impressed early in a pre-season youth tournament (2012 Vietnam Youth Cup) and then went on to play in the Sydney FC National Youth League squad.