This small finch is 4.5 to 5.5 inches in length, with a wingspan of less than 9 inches. For a finch it has a rather thin bill that is sharply pointed at the end. The tail is forked. The belly is light and the back dark but the body is strongly streaked all over. Yellow highlights on the wings and tail are distinctive when present.

The distribution is widespread across the U.S., Mexico, and Canada, with the breeding range extending into northern Canada and Alaska. The species occurs year round in western New Mexico and in the central mountain chain and throughout the western states. They will take insects. But being primarily seedeaters, Pine siskins forage in a variety of habitats offering seeds, such as yards and gardens, fields of weeds, bird feeders, and thickets. Their primary breeding habitat is coniferous forests or mixed pine/hardwood woodlands, but they move to more open fields and meadows after the breeding season ends. They travel around in flocks and actively search for seeds, often hanging upside down to reach a food source. They keep up a steady, buzzy twittering as they forage.

Females brood the 3-4 eggs in a cup nest composed of a variety of vegetation scraps and other debris, including moss, feathers, and mammal hair. Males bring food to the female and both contribute to feeding the nestlings. Pine siskins are able to survive in cold conditions due to a higher metabolic rate than other songbirds. They are also able to store and accumulate larger winter fat reserves than other finches. The female will also carefully incubate eggs and nestlings and line the nest with insulating materials to protect the young from the effects of cold.

The Audubon society reports the Pine siskin population is abundant but vulnerable to decline along the periphery of the U.S. range in western states and in central Canada, as the climate warms.