X‐ray photoelectron spectroscopy and Auger electron spectroscopy measurements were performed to investigate the initial growth mechanism and the selection of growth orientations of CdTe layers grown on (100) GaAs by metalorganic vapor phase epitaxy (MOVPE). The surface stoichiometry of the GaAs substrate was found to recover when annealed in a H2 flow atmosphere (500 °C, 5 min), although the surface was initially in an As‐rich condition after chemical etching by H2SO4 H2O2 H2O=5 1 1. No oxide was observed at both the etched and H2 annealed GaAs surfaces. Preferential adsorption of Te occurred on the GaAs surface when H2 annealing was carried out in the growth reactor in the presence of residual CdTe deposits. One monolayer of Te with a thickness of about 1.8 Å was adsorbed on the GaAs surface when the H2 annealed GaAs was exposed to diethyltelluride during the cooling period from the annealing temperature to the growth temperature (420 °C). On the other hand, minimal adsorption of Cd occurred when the H2 annealed GaAs was exposed to dimethylcadmium during the above period. (100) CdTe growth was reproducibly achieved when the GaAs surface was completely covered by one monolayer of Te before growth, otherwise (111) growth occurred. Differences in the initial growth mechanism between MOVPE and molecular‐beam epitaxy are also discussed.