This species is variable and may represent more than one species. It grows to about 30mm in length and is brown, grey or black above, often with scattered red spots. It is normally strongly marbled black and white on the ventral surface, however in some areas this marbling can be faint. There is always an orange, red or yellow patch in the armpits. This patch varies from yellow to orange between sites. At the Jervis Bay region this patch is always yellow, this may be a result of hybridisation with the Southern Toadlet (Pseudophryne dendyi) which has a strong yellow patch in the armpits. There is also a yellow/orange patch or raised bump on the back of the thigh.
The species is polyandrous, with each female mating with several males. The female visits up to eight males, mates with each, and deposits eggs in the shallow nest he has dug. The female moves on and the male tends the nest. The nest, which may contain moist leaf litter or sphagnum moss, floods during rain. The eggs hatch and the tadpoles develop in the water. If no sufficient rain happens soon after laying the eggs can remain unhatched for many weeks, with the tadpoles developing inside. The nest must stay wet so the eggs remain moist, but not too wet or they will be washed away. Female frogs that mate with more males, thus depositing eggs in more nest sites, are more likely to have some young survive.