Abstract The role of vibrational anisotropy of Mn 3+O 6 octahedron in the phase separation behavior of La 0.67− y Pr y Ca 0.33MnO 3 ( x=0, 0.15, 0.25 and 0.30) has been investigated by means of magnetization M, internal friction Q −1, Young's modulus E along with the X-ray powder diffraction measurements. For the samples with y=0 and 0.15, the Q −1 exhibits three peaks in the ferromagnetic region, which are attributed to the intrinsic inhomogeneity of ferromagnetic phase, i.e. the electronic phase separation with the coexistence of insulating and conducting phases. However, both the samples with y=0.25 and 0.30 undergo a magnetic phase separation with the coexistence of the antiferromagnetic and ferromagnetic phases, and the Q −1 peaks related to the electronic phase separation have not been observed. In addition, the Q −1 exhibits a peak in the paramagnetic region for all samples, which may result from the formation of magnetic clusters. We observed that the evolution from electronic to magnetic phase separation is close related to the rapid increase in the ratio of two kinds of Jahn–Teller distortion modes Q 3 and Q 2, i.e. Q 3/ Q 2. A schematic phase diagram is given in the text, and it is suggested that the enhancement of vibrational anisotropy of Mn 3+O 6 octahedron plays a key role in the evolution from electronic to magnetic phase separation.