The alpine newt is a medium-sized, stocky newt species.
It reaches 7–12 cm (2.8–4.7 in) length in total, females measuring roughly 1–2 cm (0.39–0.79 in) longer than males, and a body weight of 1.4–6.4 g. The tail is compressed sideways and half as long or slightly shorter than the rest of the body.
During life in water, both sexes develop a tail fin, and males a low (up to 2.5 mm), smooth-edged crest on the back.
The cloaca of males swells during breeding season.
The skin is smooth during and granular outside breeding season, and velvety during the land phase.

The characteristic dark grey to bright blue colour of the back and sides, mainly in males, is strongest during breeding season.
This base colour may vary to greenish and is more drab and mottled in females.
The belly and throat are orange and only occasionally have dark spots.
Males have a white band with black spots and a light blue flash running along the flanks, from the cheeks to the tail.
Their crest, during breeding season, is white with regular dark spots.
Juvenile efts, just after metamorphosis, resemble adult terrestrial females, but sometimes have a red or yellow line on the back.
Very rarely, leucistic individuals have been observed.

While these traits apply to the widespread nominate subspecies, I. a. alpestris, the other subspecies have slightly differing tendencies.
I. a. apuana often has dark spots on the throat and sometimes on the belly.
I. a. cyreni has a slightly rounder and larger skull than the nominate subspecies but is otherwise very similar.
In I. a. veluchiensis, females have a more greenish colour, spots on the belly, sparse dark spots on the lower tail edge, and a more narrow snout, but these differences between subspecies are not consistent.

Larvae are 7–11 mm long after hatching and grow to 3–5 cm (1.2–2.0 in) just before metamorphosis.
They initially have only two small filaments (balancers), between the eyes and gills on each side of the head, which later disappear when the fore- and then the hindlegs develop.
The larvae are light brown to yellow and initially have dark longitudinal stripes, which later dissolve into a dark pigmentation that is stronger towards the tail.
The tail is pointed and sometimes ends in a short filament.
Alpine newt larvae are more robust and have wider heads than those of the smooth newt and palmate newt.
The alpine newt is a medium-sized, stocky newt species. It reaches 7–12 cm (2.8–4.7 in) length in total, females measuring roughly 1–2 cm (0.39–0.79 in) longer than males, and a body weight of 1.4–6.4 g. The tail is compressed sideways and half as long or slightly shorter than the rest of the body. During life in water, both sexes develop a tail fin, and males a low (up to 2.5 mm), smooth-edged crest on the back. The cloaca of males swells during breeding season. The skin is smooth during and granular outside breeding season, and velvety during the land phase.
The characteristic dark grey to bright blue colour of the back and sides, mainly in males, is strongest during breeding season. This base colour may vary to greenish and is more drab and mottled in females. The belly and throat are orange and only occasionally have dark spots. Males have a white band with black spots and a light blue flash running along the flanks, from the cheeks to the tail. Their crest, during breeding season, is white with regular dark spots. Juvenile efts, just after metamorphosis, resemble adult terrestrial females, but sometimes have a red or yellow line on the back. Very rarely, leucistic individuals have been observed.
While these traits apply to the widespread nominate subspecies, I. a. alpestris, the other subspecies have slightly differing tendencies. I. a. apuana often has dark spots on the throat and sometimes on the belly. I. a. cyreni has a slightly rounder and larger skull than the nominate subspecies but is otherwise very similar. In I. a. veluchiensis, females have a more greenish colour, spots on the belly, sparse dark spots on the lower tail edge, and a more narrow snout, but these differences between subspecies are not consistent.
Larvae are 7–11 mm long after hatching and grow to 3–5 cm (1.2–2.0 in) just before metamorphosis. They initially have only two small filaments (balancers), between the eyes and gills on each side of the head, which later disappear when the fore- and then the hindlegs develop. The larvae are light brown to yellow and initially have dark longitudinal stripes, which later dissolve into a dark pigmentation that is stronger towards the tail. The tail is pointed and sometimes ends in a short filament. Alpine newt larvae are more robust and have wider heads than those of the smooth newt and palmate newt.
Alpine newt