Haylett-Petty represented Australia Under 20 in the 2008 and 2009 IRB Junior World Championships and he jointly holds the record for the most tries scored by a single player in a JWC match. His haul of 4 tries against Canada Under 20 in 2008 is equalled only by compatriots Kurtley Beale and Richard Kingi against the same opposition in 2009 and New Zealander Julian Savea against Samoa Under 20 in 2010.