A portable and adjustable trench support for placement within a trench for shoring up and maintaining the integrity of the trench walls so that workers can work safely within the trench includes a pair of support plates disposed within the trench and against the opposed trench walls, and the support plates including on their interior sides a pair of support arm guides with each support arm guide having a vertical channel and a number of offsets so that support arms can be slid within the channels and vertically positioned in the desired offsets wherein the pair of support arms mounted to the support arm guides of one support plate have larger diameters than the support arms mounted to the opposite support arm guides thereby allowing for the telescopic slidable insertion of the smaller diameter support arms into the larger diameter support arms, and then connected thereto so that the spacing of the support plates can accommodate trenches of various widths.