Thin films of CoPtCr, with 15-nm underlayers of Cr, were deposited by dc magnetron sputtering on NiP-plated aluminum substrates that were textured (anisotropic roughness) or chemically etched (isotropic roughness). The relationships between the structure and the in-plane magnetic properties were investigated. Under specific sputtering conditions, the Cr underlayer and the magnetic layer developed 〈100〉 and 〈11.0〉 crystallographic preferred orientations, respectively. The combination of 〈11.0〉 crystallographic preferred orientation and substrate texture resulted in an in-plane uniaxial magnetic anisotropy, i.e., higher squareness and coercivity parallel to the texture lines. The films with the random crystallographic orientation exhibited the in-plane magnetic isotropy on both the textured and the chemically etched Al/NiP substrates. The sputtering parameters and the substrate conditions that can lead to the development of in-plane magnetic anisotropy were specified.