Cyanate esters (CEs) are recognized as matrix materials in composites for high-temperature structural applications, owing to their excellent thermal and dimensional stability, resistance to micro-cracks, low moisture absorption, and low dielectric loss. Though the brittle nature of CEs curtails their effective utilization, thermoplastic toughening has paved the way to circumvent their innate brittle attribute by virtue of the resulting two-phase morphology. This Review enumerates detailed deliberation on thermoplastic toughening of CEs and their semi-interpenetrating networks. Further, the effects of various decisive variables like thermoplastic concentration, molecular weight, and curing conditions are also reviewed and disserted in detail. In addition, the mechanical properties of numerous developed CE blends and their toughening mechanism are deliberated to elucidate their substantial engineering applications. This Review renders a detailed contemplation on thermoplastic toughening of CEs, composite fabrication methodology, and their structural integrity for high-temperature applications.