Nests of Azure-crowned Hummingbird are reported from April in southern Mexico (Oaxaca; Rowley 1984, Binford 1989) and in February in northeastern Nicaragua (Howell 1965). Egg laying in Belize extends from February until at least the end of July (Russell 1964); a egg-laying female was collected in Tamaulipas, northeastern Mexico, in April (Martin et al. 1954) .
The nest is a small cup in a shrub or tree, 1.2-15 m above the ground. The nests in southern Mexico were placed on forks in the branches of shrubs or small trees (Rowley 1984), but two nests in Nicaragua were "saddled on a small branch" in a tree (Howell 1965). The composition of the nest varies, even at a single locality. Rowley (1984) described two differing nests from Cerro Baúl, Oaxaca: "The first was lined with hair-like particles of seed comae of an unidentified weed, some with the tiny seeds still adhering. Exteriorly it was composed of brownish plant fibers with a dead leaf and 2 pine needles attached to the bottom by the use of spider webs to form a streamer. The second nest was composed inside and out of a pinkish white down plucked from a fuzzy type of gall growth prevalenet on oaks in this area". Dimensions of the first nest were: total depth (excluding the streamer) 50 mm; external diameter, 45 mm; diameter of cup, 27 mm; depth of cup, 22 mm.
The clutch is two; the eggs are white and unmarked. Dimensions of one clutch are 14.2 x 9.0 mm and 14.2 x 9.2 mm (Rowley 1984).