Mooy posted a picture of his young fan in full Huddersfield Town kit to his Instagram account on Tuesday (AEDT).
The young girl, Bella, was taken by Mooy's appearance while watching Australia during the 2018 FIFA World Cup, which led to her liking for the Socceroos star.
"A while ago when Bella first started chemo and lost her hair she saw a World Cup player for Australia who shaves his head and was so happy because he had no hair like her," explained her Instagram post.
"His name is Aaron Mooy. I did some research and he plays in the Barkleys Premier League with the Hudderfield Town Terriers. Long story short, she now has the full kit."
