Cu-doped LaCuxMn1–xO3 perovskites have been used as a model system for a joint experimental and theoretical assessment of the influence of the Cu doping level on the structural, electronic, and magnetic properties. The different Cu-doped phases LaCu0.3Mn0.7O3 (LCM37), LaCu0.5Mn0.5O3 (LCM55), and LaCu0.7Mn0.3O3 (LCM73) including the respective Cu- and Mn-free benchmark materials La2CuO4 (LC) and LaMnO3 (LM) have been studied by magnetization measurements and electronic paramagnetic resonance. Ferromagnetic behavior was detected for pure LM and all Cu-doped perovskites, whereas antiferromagnetic behavior was revealed for La2CuO4. Generally, an increased antiferromagnetic contribution was shown for higher Cu doping levels. Equally, magnetization was highlighted to decrease with increasing Cu content. Sophisticated hybrid density functional theory calculations of the electronic and magnetic properties using defect-free, idealized Cu-doped model structures agree well with the experimental results. The findings reveal that copper incorporation influences both the electronic conductivity and the magnetic properties. Notably, the materials exhibit a tunable degree of half-metallicity and significant electronic spin polarization, establishing them as promising candidates for advanced technological applications in spintronics and catalysis. The insights gained from this study contribute to a broader understanding of perovskite materials and their versatile applications.