Objective : The purpose of this study was to determine the effects of the music therapy on cognition, problematic behavior, and sleep disturbance in elderly with dementia. Method : The study was designed using a nonequivalent control group pretest-posttest design. The subjects comprised of 39 elders (Experimental group : 19, Control group : 20) who living in D city. The instruments used for this study were the MMSE, problematic behavior assessment tool, and sleep assessment instrument. The data were analyzed using SPSS 17.0 program. Results : The repeated measure ANOVA revealed that the music therapy had the effect on the problematic behavior and sleep. There were statistically significant differences in problematic behavior between the pretest and posttest in the experimental group. Conclusion : The study suggests that the music therapy can be applied for the aged with dementia to improve the problematic behaviors.