Sleeping site selection of Brookesia decaryi was investigated in a dry forest of northwestern Madagascar from mid-October 2004 to the beginning of May 2005. Sleeping site characteristics were recorded for 304 individuals. This chameleon species is diurnal, dwelling on the ground in the daytime, but at night all individuals were found perching on small plants, shrubs, dead fallen branches, or liana. Eighty percent of adult males, 73% of adult females, 85% of juveniles, and 82% of hatchlings slept on small plants. Approximately 70% of individuals chose a sprig or branch as a support during the sleeping time; the others selected a leaf or trunk. The preferred sleeping orientation was horizontal or oblique with head up. No tendency to sleep at the tip of support was observed. There were no sexual differences in sleeping site selection (perch diameter, perch height, and vegetation height), but there were significant differences in these variables among age classes. Body size was significantly positively correlated with perch diameter and perch height, but not with vegetation height. The primary factor that determines the sleeping site and position of B. decaryi may be predation avoidance, but other factors, such as morphological constraint and climate condition, cannot be excluded.