Using synchrotron radiation, the adsorption and decomposition of propene (C3H6) on the Ni(100) surface has been investigated in situ by time-resolved and temperature-programmed x-ray photoelectron spectroscopy. At 105 K, high-resolution C 1s spectra indicate precursor mediated occupation of a single adsorption state from submonolayer to monolayer coverage with evidence of adsorbate-adsorbate interactions and dispersed phase growth. High exposures lead to the formation of multilayers which desorb above 105 K leaving a chemisorbed monolayer. Between 105 and 150 K, a shift of the binding energies in the C 1s spectra is attributed to the transition from pi- to di-sigma -bonded propene. An abrupt change in the photoemission spectra occurs at 200 K due to the conversion of di-sigma -bonded propene to a C-3 intermediate containing a methyl group. Formation of this C2HxCH3 surface species is complete at 300 K and is immediately proceeded by dehydrogenation to carbidic carbon which is the final decomposition product above 370 K.