We studied sexual dimorphism and female reproduction in Many-Lined Sun Skinks (Mabuya multifasciata) from a population in Hainan (southern China). The smallest reproductive female was 90 mm snout–vent length (SVL). The largest male was 117 mm SVL and the largest female was 116 mm SVL. To measure the potential influence of gestation temperature on female reproduction, pregnant females were maintained under five thermal conditions until they gave birth. Parturition began in early May, and females produced up to two litters per breeding season. Litter size, litter mass, and offspring size (mass) were all positively correlated with female SVL. Litter size ranged from 2–7, and it was independent of relative fecundity (litter size relative female SVL). We did not detect a trade-off between body size and offspring number. Gestation temperature affected parturition date but not litter size, litter mass, neonate mass, or relative litter mass. Females at higher (average) gestation temperatures gave birth to young earlier than did those at lower temperatures. The detrimental effects of extreme ambient temperatures on offspring body size could be buffered through maternal thermoregulation.