The end of the dry season marks the main nesting season of Highland Guans. Most nests have been found from February to May (Pullen 1983, Rowley 1984, Thurber et al. 1987, Komar 2002; K. Eisermann, personal observations), but in El Salvador an active nest was found in July (O. Komar in González-García et al. 2001). Another indication of late nesting was a female with a half-grown juvenile on 3 November 2003 at Montaña Sacranix, Alta Verapaz, Guatemala (K. Eisermann, personal observations).
Nests usually are placed in crotches of small trees and shrubs, in tangles of vines and ferns, or in the center of tree ferns, up to 15 m above ground in the forest under and midstory, and rarely also on ground (Wagner 1953, Pullen 1983, Rowley 1984, Thurber et al. 1987, González-García et al. 2001, Komar 2002, Renner 2005; K. Eisermann, personal observations). Highland Guans nest usually in old-growth forest, but rarely also in disturbed secondary growth (González-García et al. 2001).
The nest is a simple structure made of fresh and dry leafs, twigs, and rootlets lined with leafs, moss, or pine needles (Rowley 1984, González-García et al. 2001). Nest dimensions are about 30 cm outer diameter, 20 cm inner diameter, and 4.5 cm depth of the cup (Rowley 1984). Komar (2002) reported an unusual large nest with a diameter of 60 cm and depth of 40 cm.
Largest clutch size observed in nature is two eggs (Rowley 1984, Thurber et al. 1987, González-García et al. 2001; K. Eisermann, personal observations). A captive female laid 4 eggs (Calvo 1997). Eggs are white, which in the course of incubation become stained cream-colored. The average egg size is 73 x 42 mm (n = 8 eggs; Rowley 1984).
Incubation has been reported to last 25-28 days (González-García 2001), and in captivity it lasted 35 days (Calvo 1997). Only the female incubates. No data on nest success are available. Young are precocial and leave the nest as soon as they are dry, on the day of hatching or on the following day (González-García et al. 2001). Apparently the female alone rears the young (González-García et al. 2001). A female and a male were observed giving alarm calls near 2 chicks in the Chelemhá Reserve, Alta Verapaz, on 13 June 2011 (K. Eisermann, personal observations), which may indicate that males play some role in rearing young.