Spin dynamics in Fe₆₅Ni₃₅ Invar alloy has been studied by left-right asymmetry of small-angle polarized neutron scattering below T_C = 485 K in external magnetic fields of H = 0.05-0.25 T inclined relative to the incident beam. The spin-wave stiffness D and the damping Γ were obtained by fitting the antisymmetrical contribution to the scattering. The spin-wave stiffness extrapolated by a (T/T_C)^5/2 law to T = 0 K is D₀ = 117 ± 2 meVŲ, which is somewhat smaller than the spin-wave stiffness obtained by triple-axis spectrometry.