Epitaxial potassium niobate thin films were depositedinsituby low pressure metalorganic chemical vapor deposition (MOCVD) at a growth temperature of 800 °C using niobium pentaethoxide and potassium tert‐butoxide as volatile metalorganic precursors. Growth on single crystal (100) lanthanum aluminate substrates produced [110]‐oriented potassium niobate films. The films have a smooth, featureless morphology. Atomic force microscopy of the MOCVD‐derived films surface indicates a root‐mean‐square roughness of less than 2 nm. Second‐harmonic generation of 1.064 &mgr;m incident light is observed from the potassium niobate thin films, and the effective second order nonlinear susceptibilitydof the as‐deposited film is as high as 13 pm/V. ©1995 American Institute of Physics.