A modular cutting board system comprised of a plurality of cutting boards is disclosed. In this invention, individual cutting boards can be retentively conjoined to other cutting boards of the same or similar make through magnetic holding force, provided by magnets disposed in the non-working surface sides of the cutting boards, to produce a larger working surface. This invention allows for the optional use of magnetic assemblies in place of magnets alone to increase holding force and prevent magnetic interference with steel utensils. Other optional embodiments include rubber gaskets to produce watertight seals and complementary protrusions and recessions to aid in alignment at the conjoining sides. Importantly, this plurality of cutting boards can be easily detached from a conjoined state and into individual cutting boards. This quality of the present invention improves sanitation through easier cleaning and also facilitates storage, compared to large and unwieldy cutting boards.