Precise formation of connections between neurons is prerequisite for highly sophisticated brain function. Elimination of redundant synapses formed at earlier developmental stage is known as "synapse elimination" and is considered to be an essential process in neural circuit formation. The climbing fiber (CF) to Purkinje cell (PC) synapse in the cerebellum provides an ideal model for the study of developing synapse elimination. In the neonatal mouse cerebellum, each PC is innervated by multiple CFs. During postnatal development, early-formed surplus CFs are gradually eliminated and most PCs eventually become innervated by single CFs in mature mice. However, molecular mechanisms of CF synapse elimination still remain largely unknown. In this study, we examined whether brain-derived neurotrophic factor (BDNF) in postsynaptic PCs is involved in CF synapse elimination using conditional knockout mice in which BDNF is deleted in Purkinje cells (BDNF-PC-KO mice). In mutant mice, about 40% of PCs were innervated by multiple (two or three) CFs while only 20% of PCs were innervated by two CFs in control mice from postnatal day 21 (P21). These results suggest that BDNF signaling from postsynaptic Purkinje cell regulates developmental synapse elimination in the cerebellum.