Lepidodactylus lugubris is one of the most widespread geckos distributed throughout tropical Asia and the Pacific, and some populations have been introduced to seasonal subtropical areas. On tropical islands, L. lugubris reproduces throughout the year, and it is considered potentially to be a continuous breeder. Generally reproduction in lizards is greatly affected by climate, and seasonality brings a cyclic reproductive pattern. Therefore, reproduction of invasive populations of L. lugubris in a seasonal subtropical area is likely to be affected by the climate there. In this paper, I report seasonal change in size distribution of L. lugubris in northern Okinawajima Island, Ryukyu Archipelago, Japan, where the species experiences a cold winter season. In early summer, most individuals were adults, and hatchlings did not exist. In autumn, both adults and hatchlings were found, and the size distribution was bimodal (a gap exists between two groups). The change of size distribution between the two seasons may be caused by the seasonal climate, and it suggests two non-exclusive possibilities: (1) cold winter may bring quiescence of reproduction, and (2) low temperature decreases hatching success of L. lugubris in northern Okinawajima Island.