Methods are provided herein for treating agitation in a subject who has Alzheimer's disease comprising administering a VMAT2 inhibitor to a subject in need thereof. VMAT2 inhibitors useful in the methods provided herein include tetrabenazine and (S)-2-Amino-3-methyl-butyric acid (2R,3R,11bR)-3-isobutyl-9,10-dimethoxy-1,3,4,6,7,11b-hexahydro-2H-pyrido[2,1-a]isoquinolin-2-yl ester.