An expandable trailer comprising a chassis, at least one pair of extendable supports, at least one pair of horizontal floor sections and at least one pair of floor elements. Each support is extendable laterally outwardly to a respective side of a central longitudinal axis of the chassis. The horizontal floor sections of each pair of horizontal floor sections are spaced apart laterally and each have an outer rail which is coupled to a corresponding one of the supports. The floor elements are pivotally coupled to each other and to the floor sections. Upon extension of the extendable supports from a retracted position to an open, extended position, the horizontal floor sections move laterally outwardly to extend from the chassis and the floor elements move from an upright vertical arrangement to an arrangement where the floor elements lie in horizontal alignment with the floor sections.