We have observed the Fraunhofer diffraction pattern of x‐rays exiting from the end face of a SiO2/polyimide/Si thin‐film waveguide. The measured angular intensity distributions are in excellent agreement with those calculated based on the dimensions and the refractive index profile of the guide. Our measurement confirms that, at the end face of the guide, the wavefront of a single guided mode is fully coherent in the direction normal to the guiding plane. This focused and transversely coherent x‐ray beam may be used as a source for coherence‐based experiments, such as x‐ray photon correlation spectroscopy. ©1995 American Institute of Physics.