The ID1 gene regulates a leaf-generated signal required for the transition to flowering in maize. Like ID1, the OsID1 gene acts as a master switch for the transition from the vegetative to the reproductive phase in rice. In this study, an ID1 ortholog, BmID1, was isolated from Bambusa multiplex. The ORF of BmID1 was 1182-bp long, and encoded a peptide of 393 amino acids containing a putative NLS, four zinc finger motifs, and a conserved TRDFLG motif at the C terminal. BmID1 shared 64.9 % identity with the ID1 ortholog in Zea mays and 62.16 % with the ID1 ortholog in Oryza sativa. BmID1 was expressed very weakly in the developing leaves and shoots of flowering plants, but not in those of non-flowering plants. Unlike OsID1, BmID1 was expressed with a circadian rhythm. The BmID1 protein localized to the nucleus, suggesting that it might act as a transcription factor to regulate flowering in bamboo.