In order to provide new phase relations for a thermodynamic modeling, eight binary B-Ce alloys were experimentally examined by means of differential thermal analysis, electron probe microanalyzer and X-ray diffraction methods Reassessment of the binary B-Ce system was then performed based on the experimental data from this work and literature data by using the CALPHAD method. Reasonable agreement between experimental data and the calculated phase diagrams has been reached. Subsequently, the phase equilibria of the B-Ce-Cu system was calculated based on the present thermodynamic description of the B-Ce system, the previous descriptions for the B-Cu and Ce-Cu systems as well as the experimental data from the literature. The isothermal sections at 400 and 600 degrees C, liquidus projection with invariant reactions were calculated and presented in this work.