We investigated the effect of nanopores on the adhesion behavior at polymer-metal interfaces by molecular dynamics simulation. The effects of shear and extension behavior were examined. In the shear mode, samples with porous substrates showed larger shear forces than those with flat substrates. Meanwhile, the breaking strengths in the extension mode were almost the same for systems with flat and porous substrates. The similar behavior in the extension mode was ascribed to the formation of voids in the polymer layer, which was related to the increase of total system volume and not affected by the presence of pores. We also investigated the relationship between the mechanical properties of polymer-metal interfaces in the shear mode and pore size in detail. Even a very shallow pore with a depth of 0.5 nm produced a large shear force comparable to that of a pore with a depth of 2.0 nm. The shear force increased gradually as the pore diameter became wider. These simulation results revealed that the adhesion forces between polymers and rough metal surfaces are not simply related to the interface area but depend on the pulling mode, pore size, and polymer chain length in a complicated manner.