Electromagnetic properties of complex oxide solid solutions containing Ce and Y attract increasing interests due to their high application potential. Their properties are known to be dependent on many factors including grain size and crystal defects. Here we focus on unique features of nanocrystalline solid solutions prepared via a mechanosynthesis. Mechanically activated and mechanosynthesized exhibit room-temperature ferromagnetism. The saturation magnetization reaches maximum for the solid solution. XPS and Raman spectra show that Ce4+ ions are partially reduced to Ce3+, with simultaneous introduction of oxygen vacancies accumulated on surface of the solid solutions. An analysis of the experimental magnetization data and the determination of both the spin state and the concentration of magnetic carriers revealed that a small part of the Ce3+ spins (<1%)is responsible for the magnetic state of the system. Existence of clusters with a short-range antiferromagnetic order is also suspected.