The present study reports the development of thermally stable, sustainable vanillin–guaiacol-based multifunctional cyanate ester–epoxy hybrid blend and silicon carbide (SiC) reinforced composites for high-performance applications. A bio-based cyanate ester (VGCE) was synthesized from vanillin and guaiacol-derived trisphenol and subsequently hybridized with epoxy (VGEP) to obtain VGCE/VGEP hybrid systems. The curing temperature of VGCE and VGCE/EP (1:1, w/w) hybrid blend obtained in the presence of varied wt.% of copper (II) acetylacetonate are 127°C and 139°C, respectively. The hybrid systems exhibited excellent thermal stability (10% weight loss at 369°C) and low dielectric constants (2.9–3.2 at 1 MHz) with minimal dielectric loss (0.025–0.035 at 1 MHz). Both VGCE and VGCE/EP blend displayed hydrophobic surfaces with the value of water contact angle above 120° and very low moisture uptake (< 0.01%). An incorporation of 20 wt.% SiC further improved thermal performance, char residue of 51.9% and an exceptionally low coefficient of thermal expansion of 8.78 × 10−6/°C. SEM micrographs confirmed uniform dispersion of SiC particles without interfacial voids, while XRD revealed the crystalline contribution of SiC within the amorphous polymer matrix. XPS analysis confirms the strong interfacial interactions occurred between the filler and hybrid matrix. Results from different studies suggest that the bio-based cyanate ester–epoxy hybrid matrices and their SiC reinforced composites can be considered for thermally stable low out-gassing microelectronics insulation applications. © 2026 Society of Plastics Engineers.