We systematically explored the indentation size effect (ISE), which is not expected to occur in non-crystalline materials due to the absence of dislocations and strain hardening, in bulk metallic glass (BMG). A series of nanoindentation experiments with different indenters result in somewhat surprising observations that show that ISE clearly does exist in BMG and can even be described by the ISE model for crystalline materials. The results are discussed in terms of possible mechanisms responsible for the ISE in BMG.