Almost all information on the breeding of White-chinned Swift is from Marín and Stiles (1992; Costa Rica); see also Whittaker and Whittaker (2008; Brazil).
Breeding (egg laying) in Costa Rica is from early May to early June. Nests in Brazil contained eggs and juveniles in late July. The nest is placed on rock walls behind or near waterfalls, where the nest and the substrate are constantly wet from spray. The nest is sited in a narrow crack or on a small ledge or knob under an overhang. The nest also usually is screened by overhanging vegetation, most commonly by Pilea but sometimes by mosses or liverworts. The nest is a shallow cup, primarily composed of bryophytes (mosses and liverworts), with a mud base.
The clutch is one, and the egg is dull white. Dimensions of the egg are 28,23 x 19.41 mm (n = 1; Marín and Stiles 1992). The lengths of the incubation and nestling periods are unknown; Marín and Stiles (1992) estimate the incubation period as ca 30 days. The nestling period is 55-58 days (Marín and Stiles 1992).