Photophysical and singlet oxygen sensitization processes of 5,10,15,20-tetrakis(4-trimethylsilylphenyl)porphyrin have been studied. It was found out that the quantum yield (Phi(Delta)) of singlet oxygen production increased by the silylation of 5,10,15,20-tetraphenylporphyrin (TPP). The silylation does not affect the photophysical processes of TPP but enhances the sensitization efficiency of singlet oxygen by the triplet sensitizer (f(Delta)(T)). This enhancement can be explained by the suppression of the process from the triplet encounter complex composed of the triplet sensitizer and ground-state oxygen to the ground-state sensitizer and oxygen.