We report inelastic light scattering experiments on superconductor Ce0.6Y0.4FeAsO0.8F0.2 from 4K to 300K covering the superconducting transition temperature Tc ∼ 48.6K. A strong evidence of the superconductivity induced phonon renormalization for the A1g phonon mode near 150cm-1 associated with the Ce/Y vibrations is observed as reflected in the anomalous red-shift and decrease in the linewidth below Tc. Invoking the coupling of this mode with the superconducting gap, the superconducting gap (2Δ) at zero temperature is estimated to be ∼ 20meV i.e the ratio 2Δ(0)/kBTc is ∼ 5, suggesting Ce0.6Y0.4FeAsO0.8F0.2 to belong to the class of strong coupling superconductors. In addition, the mode near 430cm-1 associated with Ce3+ crystal field excitation also shows anomalous increase in its linewidth below Tc suggesting strong coupling between crystal field excitation and the superconducting quasi-particles. © 2014 AIP Publishing LLC.