The house sparrow is typically about 16 cm long, ranging from 14 to 18 cm). The house sparrow is a compact bird with a full chest and a large, rounded head. Its bill is stout and conical with a culmen length of 1.1–1.5 cm, strongly built as an adaptation for eating seeds. Wingspan ranges from 19–25 centimetres. The plumage of the house sparrow is mostly different shades of grey and brown. The sexes exhibit strong dimorphism: the female is mostly buffish above and below, while the male has boldly coloured head markings, a reddish back, and grey underparts. The female has no black markings or grey crown, juveniles are similar to the adult female, but deeper brown below and paler above.

The house sparrow is strongly associated with human habitation, and can live in urban or rural settings. Though found in widely varied habitats and climates, it typically avoids extensive woodlands, grasslands, and deserts away from human development. It feeds mostly on the seeds of grains and weeds, but it is an opportunistic eater and commonly eats insects and many other foods. Its predators include domestic cats, hawks, and many other predatory birds and mammals.

It roosts communally and while breeding nests are usually grouped together in clumps. House sparrows also engage in social activities such as dust or water bathing and "social singing", in which birds call together in bushes.