We studied reproduction and nesting of the keeled box turtle (Cuora mouhotii) during 2003 and 2009 on Hainan Island, China. We found the first gravid turtle on 28 April and nesting was from May until July, with a peak in mid-June. We observed the first fresh nest on 1 June and last fresh nest on 27 July. Some females laid eggs from 1 clutch in 2 batches. Clutch size ranged from 1 to 5. Mean egg measurements were as follows: length, 4.5 cm; width, 2.7 cm; and mass, 19.8 g. There was no significant relationship between turtle body size (mass, length, height, and width) and clutch size or egg size (mass, length, and width). Clutch size was significantly correlated with the egg mass and egg width. Possible low fertility, low hatching rate, and the long period to reach maturity imply that C. mouhotii has a low intrinsic rate of population increase. This, combined with overcollecting and habitat destruction, requires development of more effective conservation strategies for this endangered species.