Magnetic, transport, and thermal properties of metallic η-carbides Co6M6C and Ni6M6C (M=Mo and W) with the cubic Ni6Mo6C-type structure have been characterized. The Ni-based compounds Ni6Mo6C and Ni6W6C are Pauli paramagnets with temperature-independent susceptibilities. Susceptibilities of the Co-based compounds Co6Mo6C and Co6W6C are enhanced and temperature-dependent. Co6Mo6C remains paramagnetic down to the lowest temperature, while Co6W6C undergoes an antiferromagnetic-type transition at 46K. A metamagnetic transition was observed for Co6W6C at 20–30T at the lowest temperatures. The correlation among the enhancements in the susceptibility, the resistivity, and the electronic specific heat suggests the presence of moderate electron correlation in these compounds.