It has been seen at bird feeders in both seasons, with occasional birds overwintering near a bird feeder. The bird is most commonly found in the western Upper Peninsula, and is probably a regular migrant there. The Harris' Sparrow breeds along the northern limit of the tree line south of the arctic tundra. The birds arrive there throughout May and nest from mid-June through early July. Nesting is in stunted coniferous forests, often in open spruce stands near moist bogs.
Nests are on the ground and well concealed among reindeer lichens, Labrador tea, or small shrubs.
The nest is a bulky cup made of dead grass, rootlets, and mosses, and is lined with fine grasses, sedges, and sometimes the hair of animals such as caribou. A typical clutch consists of 3 to 5 pale green eggs blotched with brown. Incubation is done exclusively by the female and takes from 1314 days. Both male and female attend the young. Age at fledging has not been determined.