We estimated the outcrossing rates at small-scale flowering sites of an endemic dwarf bamboo species, Sasa cernua. The multi-locus estimation of the outcrossing rate of the dwarf bamboo population was 0.148 (SD 0.118). Two culms with the highest outcrossing rates had heterozygous genotypes at one locus, but other culms in the locus were homozygotes. Five culms with high outcrossing rates bore 2-17% seeds with homozygous genotypes. Due to predominant selfing, the overall inbreeding coefficient of seeds was high, although it declined in seedlings. This suggests that selection against inbred progenies began early in the establishment process in the natural habitat.