The American redstart was described by Carl Linnaeus in 1758 in the 10th edition of his Systema Naturae under the binomial name Motacilla ruticilla.

[2] The genus name Setophaga is from Ancient Greek σής : sēs (genitive σητός : sētós) "moth", and φάγος : phágos "eater".

[8] The breeding males are unmistakable, jet black above apart from large orange-red patches on their wings and tails.

In their other plumages, American redstarts display green in their upperparts, along with black central tails and grey heads.

It is insectivorous, often sharing its foraging habitats with other warblers, and is found feeding in the mid to lower regions of a tree or shrub.

On its wintering grounds in Central and South America, the redstart may be found in nearly all woody habitats but tends to avoid non-forested agricultural areas.

[14][15] American redstarts display a mixed mating strategy; they are predominantly monogamous but around 25% of males maintain multiple territories and are polygynous.

The intensity of the male's coloration (which is due to carotenoid pigments) predicts their success at holding territory in their non-breeding, winter locations in the Caribbean, the probability that they will be polygynous, and the proportion of offspring in their nests that they will themselves father.

Overall, this species is a very flexible, opportunistic feeder that can easily adapt to varying habitat, season, insect community, vegetation structure, and time of day.

The diet consists largely of caterpillars, moths, flies, leafhoppers and planthoppers, small wasps, beetles, aphids, stoneflies and spiders.

[15][17] Successful conservation efforts of the redstart, as for any other migrating bird, include protecting and providing habitat throughout its entire range.

[19] Still, the most effective method for American redstart conservation would be natural habitat preservation at wintering and breeding grounds.