This slug species occurs on the east coast of Australia, from New South Wales to Queensland.

Red triangle slugs are found in damp situations in various habitats, including city gardens, forests, woodland and heaths.

[2] These slugs graze on algae which grows on the surface of the smooth bark of some eucalyptus trees and on rocks.

Individual slugs can be white, off-white, yellow, dark or light grey, beige, pink, red, or olive green.

[4] Various shots of Triboniophorus graeffei on the bark of Sydney Blue Gums, near Dungog, Australia, showing color variation, varying degrees of contraction and body shape.