The initial stage of epitaxial growth of GaP on Si by low‐pressure metalorganic chemical vapor deposition was characterized by transmission electron microscopy. The growth mode changes from three‐dimensional to two‐dimensional with increasing V/III ratio. GaP on Si grown at a low V/III ratio of 800 contains many dislocations, stacking faults, and microtwins; however, a significant reduction in the density of these defects is observed in GaP grown at high V/III ratio of 3200.