We have studied the ferromagnetism and spin-glass-like behavior in polycrystalline perovskite (Nd0.65Y0.35)0.7Sr0.3MnO3 based on investigations of the magnetization, magnetic AC susceptibility, and electron spin resonance (ESR). Magnetization measurements versus temperature reveal a spin-glass phase-transition temperature T g at about 53 K. For the in-phase susceptibility x′(T), a frequency-dependent peak called the spin-freezing temperature T f is observed. A lowering of the frequency to zero leads to T f → T g . The dynamics of this process was analyzed by means of the slowing-down scaling law τ/τ o = (T f /T g -1) −zv , where the characteristic time τ o and critical exponent zv obtained by fitting the experimental T f data were about (i.e., 1.6 × 10−15 s) and 10.12, respectively, quite different from those expected for canonical spin-glass systems with τ o = 10−13 s and zv = 10. The spin-glass phenomenon is related to the magnetic frustration phenomenon caused by strong competition between ferromagnetic and anti-ferromagnetic interactions, together with the strong magnetic disorder. The dynamics of the magnetic interactions in (Nd0.65Y0.35)0.7Sr0.3MnO3 was studied further by means of ESR.