Boron nitride nanoplatelet (BNNP) with superior mechanical properties can be a promising candidate as reinforcement to improve the toughness of glass‐ceramics. In this paper, glass‐ceramics composites reinforced with well‐dispersed BNNPs have been fabricated by spark plasma sintering. The addition of BNNP enhances the mechanical properties of glass‐ceramics and inhibits the nucleation and growth of the diopside. The number of diopsides and the grain size gradually decrease with the increase of BNNP content. The mere addition of 1.0 wt.% BNNPs can simultaneously increase the hardness and fracture toughness by 7.94 % and 22.54 %, respectively. Crack deflection, BNNP pull‐out, crack blocking, and crack bridging are the main toughening mechanisms, and the toughening model was established to optimize the design of BNNP reinforced composites.This article is protected by copyright. All rights reserved.