This work introduces a simple and facile approach for the morphology and size controlled synthesis of Co-doped MIL-96. By using different bases as modulators, Co-doped MIL-96 was obtained with sizes that varied from 5 μm to 300 nm, and four different morphologies, including hexagonal prism, icosahedron, hexagonal spindle and ellipsoid. Among these, nano-sized Co-doped MIL-96 with an ellipsoid morphology exhibited the highest electroactive surface area and good conductivity as well as the best electrochemical sensing performance towards α-fetoprotein.