Visible light-induced oxygen atom transfer from NO2 to propene has been investigated in low-temperature argon and xenon matrices. The reaction intermediate was propyl nitrite radical, and the final products were methyloxirane and NO, which was confirmed by FT-IR spectroscopy. Conformational structure of propyl nitrite radical was determined by the vibrational analysis of N=O and N-O stretching modes for the normal and O-18-isotope-substituted species with the aid of ab initio calculations, where geometrical optimization was carried out by using the DFT method with the 6-31G* basis set. From the analysis of absorbance growth behavior of the infrared bands for propyl nitrite radical and methyloxirane, first-order rate constants were determined by least-squares fittings. The photoreaction of propene and NO2 in xenon matrices was found to occur more rapidly than in argon matrices. The wavelength dependence of the rate constants is also discussed.