This cave salamander is most notable for its adaptations to a life of complete darkness in its underground habitat. The olm's eyes are undeveloped, leaving it blind, while its other senses, particularly those of smell and hearing, are acutely developed. It also lacks any pigmentation in its skin. It has three toes on its forelimbs, but only two toes on its hind feet.
Longevity is estimated at up to 58 years. A study published in Biology Letters estimated that they have a maximum lifespan of over 100 years and that the lifespan of an average adult is around 68.5 years.