The northern pintail is a fairly large duck with a wing chord of 23.6–28.2 cm (9.3–11.1 in) and wingspan of 80–95 cm (31–37 in).
The male is 59–76 cm (23–30 in) in length and weighs 450–1,360 g (0.99–3.00 lb), and therefore is considerably larger than the female, which is 51–64 cm (20–25 in) long and weighs 454–1,135 g (1.001–2.502 lb).
The northern pintail broadly overlaps in size with the similarly-widespread mallard, but is more slender, elongated and gracile, with a relatively longer neck and (in males) a longer tail.
The unmistakable breeding plumaged male has a chocolate-brown head and white breast with a white stripe extending up the side of the neck.
Its upperparts and sides are grey, but elongated grey feathers with black central stripes are draped across the back from the shoulder area.
The vent area is yellow, contrasting with the black underside of the tail, which has the central feathers elongated to as much as 10 cm (3.9 in).
The bill is bluish and the legs are blue-grey.

The adult female is mainly scalloped and mottled in light brown with a more uniformly grey-brown head, and its pointed tail is shorter than the male's; it is still easily identified by its shape, long neck, and long grey bill.
In non-breeding (eclipse) plumage, the drake pintail looks similar to the female, but retains the male upperwing pattern and long grey shoulder feathers.
Juvenile birds resemble the female, but are less neatly scalloped and have a duller brown speculum with a narrower trailing edge.

The pintail walks well on land, and swims well.
It has a very fast flight, with its wings slightly swept-back, rather than straight out from the body like other ducks.
In flight, the male shows a black speculum bordered white at the rear and pale rufous at the front, whereas the female's speculum is dark brown bordered with white, narrowly at the front edge but very prominently at the rear, being visible at a distance of 1,600 m (0.99 mi).

The male's call is a soft proop-proop whistle, similar to that of the common teal, whereas the female has a mallard-like descending quack, and a low croak when flushed.
The northern pintail is a fairly large duck with a wing chord of 23.6–28.2 cm (9.3–11.1 in) and wingspan of 80–95 cm (31–37 in). The male is 59–76 cm (23–30 in) in length and weighs 450–1,360 g (0.99–3.00 lb), and therefore is considerably larger than the female, which is 51–64 cm (20–25 in) long and weighs 454–1,135 g (1.001–2.502 lb). The northern pintail broadly overlaps in size with the similarly-widespread mallard, but is more slender, elongated and gracile, with a relatively longer neck and (in males) a longer tail. The unmistakable breeding plumaged male has a chocolate-brown head and white breast with a white stripe extending up the side of the neck. Its upperparts and sides are grey, but elongated grey feathers with black central stripes are draped across the back from the shoulder area. The vent area is yellow, contrasting with the black underside of the tail, which has the central feathers elongated to as much as 10 cm (3.9 in). The bill is bluish and the legs are blue-grey.
The adult female is mainly scalloped and mottled in light brown with a more uniformly grey-brown head, and its pointed tail is shorter than the male's; it is still easily identified by its shape, long neck, and long grey bill. In non-breeding (eclipse) plumage, the drake pintail looks similar to the female, but retains the male upperwing pattern and long grey shoulder feathers. Juvenile birds resemble the female, but are less neatly scalloped and have a duller brown speculum with a narrower trailing edge.
The pintail walks well on land, and swims well. It has a very fast flight, with its wings slightly swept-back, rather than straight out from the body like other ducks. In flight, the male shows a black speculum bordered white at the rear and pale rufous at the front, whereas the female's speculum is dark brown bordered with white, narrowly at the front edge but very prominently at the rear, being visible at a distance of 1,600 m (0.99 mi).
The male's call is a soft proop-proop whistle, similar to that of the common teal, whereas the female has a mallard-like descending quack, and a low croak when flushed.
Northern pintail