Disclosed herein is an apparatus for transporting sets of items at different temperatures using a modular system, which comprises a cooler, a detachable tote, and a means of securely affixing the tote to the top of the cooler for facilitating compact portability. In more detail, the Modular Cooler Apparatus and System invention comprises a soft-sided cooler comprising an insulated base and an insulated lid that connect together in a sealable fashion using a water proof zipper, lower strap connection points, and connecting support straps with connectors; a detachable soft-sided tote comprising a waterproof polyester exterior, a pocket, handle straps, upper strap connection points; and connecting straps comprising webbing, stitched loops, and tension locks with gates, which securely bind the detachable tote pack to the top of the cooler in a well-balanced fashion.