Member of the finch family: These birds are fairly small, being around the same size as the widespread American goldfinch. In both sexes, total length can range from 11–14 cm (4.3–5.5 in), with a wingspan of 18–22 cm (7.1–8.7 in) and weight of 12–18 g

Adults are brown on the upperparts and pale on the underparts, with heavy streaking throughout. They have short forked tails. Their bills are conical like most finches but are more elongated and slender than those of other co-occurring finches. Variably, pine siskins have yellow patches on their wings and tails, which may also consist of white streaks on the wings.