Huia cavitympanum lives in hillside primary forests. It is associated with rocky, clean and mountain streams. The species has been recorded from approximately 250 to 1000 m a.s.l. 

H. cavitympanum is easy to recognize: the eardrum is sunken in, the body coloration is contrasty, the legs are long, the belly is yellow. The back is chocolate brown and separated by beige or sometimes orange longitudinal strips from the lighter flank. The shank bears a yellow or orange longitudinal line above. The limbs have distinct dark cross-bands. The iris is beige in the upper third and red in the lower two thirds. Finger and toe tips are expanded and form adhesive discs. Males are approx. 50 mm, females 80 mm in snout-vent length (SVL).

Reproduction takes place in clear, rocky streams that are big enough to form torrential, foaming cascades. The spectacular tadpoles of this species live in very fast flowing waters. They cling to rock faces by their huge, strong abdominal sucker. The body shape is very streamlined. The tail is very strong and muscular. Tadpoles reach 70 mm in length.