Sirtuin 1 is a nicotinamide adenine dinucleotide-dependent protein deacetylase which regulates longevity and improves metabolism. Activation of Sirtuin 1 confers beneficial effects in models of neurodegenerative diseases. We and others have provided convincing evidence that overexpression of Sirtuin 1 plays a neuroprotective role in mouse models of Huntington's disease. In this study, we report that SRT2104, a small molecule Sirtuin 1 activator, penetrated the blood-brain barrier, attenuated brain atrophy, improved motor function, and extended survival in a mouse model of Huntington's disease. These findings imply a novel therapeutic strategy for Huntington's disease by targeting Sirtuin 1.