A modular wall system is an easily assembled or disassembled wall or partition having connectable block sections that connect together on any side edge to form a wall. The side edges have slotted openings for conduit or wiring to pass through, and contact brackets that are linearly adjustable in length attach to the top, side, or bottom of the formed wall to fill in the space and attach to an existing wall, ceiling, or floor. The block sections have panels that cover the open spaces on front and back once erected.