Dynamic methylation/demethylation of histones and non-histone proteins occurs during the cell cycle. Lysine-specific demethylase 1 (LSD1) exhibits diverse transcriptional activities through catalyzing demethylation of mono- and di-methylated histone H3 on lysine 4 (H3K4) and lysine 9 (H3K9). We show here that inhibition of LSD1 expression by siRNA leads to abnormal chromosomal segregation in unperturbed mitosis and abnormal centrosome duplication, and is associated with decreased protein levels of MAD2 and BUBR1. LSD1 positively regulates the BUBR1 and MAD2 promoter activity and maintains local monomethylation status of H3K9, which is a repressive histone mark for gene transcription. Expression of exogenous BUBR1 and MAD2 in LSD1-depleted cells partially rescues the defect of chromosome segregation. Our results suggest that LSD1 plays a role in chromosomal segregation during mitosis partially through transcriptional regulation of BUBR1 and MAD2.