Abstract: A seismic support system for supporting and restraining a water heater against both horizontal and vertical displacement in the event of an earthquake. The seismic support system comprises three principle components including: a bracket assembly including primary length-adjustable bracing arms for bracing an upper perimeter portion of the water heater to a nearby wall or walls; an adjustable and collapsible stand assembly for elevating the water heater above a floor surface; and plural spaced apart vertically oriented connecting members which surround and cradle the water heater and join the water heater stand assembly to the bracket assembly. Secondary bracing members are also provided to the bracket assembly extending between the primary bracing arms and the wall and/or opposite ends of the primary bracing arms in cross member fashion to provide additional rigidity. The stand assembly includes height-adjustable foot members to adapt the stand assembly to uneven floor surfaces.