The crystallization behavior and mechanism of CaO–Al2O3–MgO–SiO2 (CAMS)-based diopside glass ceramics with nano-ZrO2 nucleators and CeO2 agents have been investigated. The use of nanoscale ZrO2 as nucleators is favorable to the crystallization of glass ceramic at a relatively lower temperature due to the reduction of the activation energy, while the activation energy is increased after adding the CeO2 agent. The microstructure and orientation have been analyzed by scanning electron microscopy and electron backscatter diffraction. Two disceible layers are observed, featured in glass and crystalline phases, respectively. Remarkably textured polycrystalline diopsides are verified for the samples (A and B) free of CeO2 agents, with c-axes perpendicular to the interface of the two layers. Comparatively, the c-axes of diopside grains of the sample (C) with CeO2 agents are proved to be parallel to the interface. Nanocrystals are detected in the vicinity of the interface for sample C.