The substitution of magnetic Fe2+ for nonmagnetic Cu+ in the Cu1−xFexIr2S4 system causes drastic changes in electromagnetic behavior. Forx = 0.01 and 0.025, the Peierls-like phase transition stepΔM in magnetizationincreases with x increasing, and an unexpected spin transition occurs atT*≈120 K. This may be attributed to the spin-polarization of theIr4+ ions bythe Fe2+ ions.When x exceed 0.1, the Peierls-like phase transition is suppressed completely. Themagnetic state for Fe doped samples transforms from ferromagnetic (FM) toparamagnetic (PM), and back to the FM state again with the increase ofx. For the highly doped samples, the FM domains formed byFe2+ ions result inanother transition at T**≈110 K and the cluster–spin glass transition.