We report on the breeding biology of the White-throated Woodcreeper (Xiphocolaptes albicollis), a species endemic to the Atlantic forest of South America, based on 16 nesting attempts in 11 cavities (9 natural tree cavities and 2 nest boxes) in Misiones, northeastern Argentina. Natural cavities were 3.3–8.3 cm in diameter and 46–103 cm in depth, and generated by decay processes (not woodpeckers) at heights of 3–17 m in live trees 29–106 cm in diameter at breast height. White-throated Woodcreepers laid 2–4 eggs on alternate days, on a bed comprised of bark flakes, leaf fragments and seed pods. Incubation bouts (n  =  3) were more than 1 hr 40 mins. Incubation lasted 17 days and the nestling period 18–22 days, shorter than the congeneric Great Rufous Woodcreeper (Xiphocolaptes major). Both adults brought nest material, incubated the eggs, fed the nestlings, and removed fecal sacs; however, we suspect that the male contributed more to fecal sac removal. Both adults roosted in the cavity a few nights before eggs were laid, but only one adult did so during the incubation and nestling periods. Nestlings were fed arthropods and small vertebrates at an average rate of 3 visits/hr with no change in delivery rate over the nestling period. Adults defended their nests from four bird species but shared one cavity with a roosting female Helmeted Woodpecker (Dryocopus galeatus) throughout their incubation period. We confirm that the White-throated Woodcreeper exhibits biparental care like the Great Rufous Woodcreeper, the Dendrocolaptes and the Lepidocolaptes, but in contrast to Sittasomus, Dendrocincla and Xiphorhynchus. We recommend studies with banded individuals to determine the relative contribution of each parent.