Moffatt has been a gallery artist, art teacher, cartoonist and children's books author and illustrator, as well as working at times as a shop assistant, house painter, radio operator, factory worker, police officer and publisher's representative.
Moffatt completed a house-painting apprenticeship before studying art by correspondence, and in the late 1960s he launched his artistic career by selling black and white line drawings in Brisbane. He has since held many art exhibitions. He moved into publishing, and then, in the 1980s, took his love of children and art to Queensland schools, with the assistance of the Queensland Arts Council. He would sing to the children, read to them and tell them stories, drawing and mimicking people as he did so.
When Moffatt writes he has often used songs lyrics as a starting point, and has used lyrics by Bob Dylan, John Lennon and BB King for his inspiration.