Using density-functional theory, we show that the NiAs-type is a more favorable structure for the (W0.5Al0.5)C phase than the experimentally proposed WC-type structure when we compare the thermodynamic, dynamic and elastic properties of the two types. Furthermore, it is found that this NiAs-type (W0.5Al0.5)C phase could be synthesized under pressures of 12 GPa or higher, while the advanced mechanical properties of the (W0.5Al0.5)C phase, including the bulk modulus of B = 268 GPa, the shear modulus of G = 206 GPa, and the hardness of HV = 30 GPa, could be reproduced by the NiAs-type structure. The fantastic mechanical properties of the phase are attributed to the synergistic effect of stronger C–Al bonding and weaker C–W bonding of the NiAs-type structure.