Red-breasted Nuthatches are almost always found in conifer trees, where they live in pairs. Often, one can hear the male and female "talking softly" to each other with single, nasal-sounding contact notes, while they forage a few meters apart along the trunks and branches of pine or spruce trees.

Male Red-breasted Nuthatches have a black crown and nape. The lores, the supercilium, and the sides of the mantle are white. A black eyestripe broadens backward to the sides of the mantle. The chin, cheeks, ear coverts, and sides of the upper neck are white. The upperparts, lesser and median coverts, and central tail feathers are gray-blue. The outer 4 tail feathers have white centers, and the outer 3 have gray-blue tips. The primaries, secondaries, tertials, and alula are dark gray-brown. The lower neck, breast, flanks, belly, vent, and undertail coverts are rusty-cinnamon. The upper mandible is black, the lower is pale gray, and the legs and feet are dusky.

Females are similar to males, but the crown and nape and eyestripe are dark gray, not black; the eyestripe is variable but usually paler than in males. Underparts are paler, not as richly colored as males.

In the past, Red-breasted Nuthatches' migration patterns have been irruptive: some years they've headed south, some years they haven't. During irruption years their southerly migration may begin as early as late summer and extend through fall and winter.