Harvesting　vibration　energy　using　piezoelectric　materials　has　gained　considerable　attention　over　the　past　few　years.　Typically,　a　piezoelectric　energy　harvester　is　a　unimorph　or　bimorph　cantilevered　beam　which　undergoes　base　vibration.　The　focus　of　this　paper　is　to　compare　the　Euler-Bernoulli　model　and　the　Timoshenko　model,　which　are　both　used　for　modeling　the　vibration-based　energy　harvester.　Procedures　of　deriving　the　electro-mechanical　equation　of　motion　are　provided,　following　exact　expressions　for　the　electrical　output　in　two　models.　Parametric　case　studies　are　carried　out　in　order　to　compare　the　frequency　response　of　two　models.　Simulation　results　show　that　there　is　a　great　difference　between　Euler-Bernoulli　model　and　Timoshenko　model　at　low　length-to-thickness　aspect　ratio.　Such　difference　diminishes　and　becomes　negligible　as　aspect　ratio　increases.　It　is　shown　that　for　the　design　of　piezoelectric　energy　harvester　with　small　aspect　ratio,　Timoshenko　model　can　be　more　accurate　than　Euler-Bernoulli　model　in　predicting　the　system　behavior.　©　2011　by　ASME.