Abstract An incorporation of the LDA+U formalism into the spin-polarized relativistic Korringa–Kohn–Rostoker (SPR-KKR) method of band-structure calculations is presented. This new approach accounts for one-particle relativistic effects in a proper way when applying the LDA+U method to get an improved description of correlation effects compared to plain LDA-based calculations. In addition, it allows to deal with disordered systems in a straight forward manner by a combination with the coherent potential approximation (CPA) alloy theory. These features are demonstrated by results obtained for fictitious ferromagnetic fcc-Uranium and the disordered alloy system FexCo1−x.