The phase diagram for the CuBr-CsBr system has been determined using differential scanning calorimetry and X-ray diffraction. The occurrence of three intermediate compounds has been shown: Cs2CuBr3, melting incongruently at 635 K; CsCu2Br3, melting congruently at 636 K and CsCu19Br20, melting incongruently at 624 K and decomposing in the solid state at 562 K. The coordinates of two eutectic points are 589 K, 48 mol% CsBr and 575 K, 21 mol% CsBr.