Males sing a series of high, sweet whistled notes, generally falling slightly in pitch overall, often with clearer notes followed by more complex patterns. A song lasts about 1–2 seconds. There are many song dialects, each shared by many males, but each male sings only one. Singing begins in late winter before the spring migration.
When feeding or foraging in flocks, American Tree Sparrows toss back and forth a musical twitter, sometimes described as a teel-wit or teedle-eet, which may vary from flock to flock. Alarmed, they give a hard tseet. In flight, they make a softer tsiew. Females solicit copulation with a whey-whey-whey while fluttering their wings and raising their tails.