<p>Phthalonitrile (PN) resins are high-performance thermosetting polymers recognized for their exceptional thermal stability and flame resistance, making them attractive candidates for aerospace, electronics, and high-temperature structural applications. However, their broader adoption is hindered by two primary challenges: the high melting point of PN precursors and the volatility of conventional curing agents, which complicate processing and raise safety concerns. Despite ongoing research, effective strategies that simultaneously address these issues while enhancing the overall performance of PN resins remain limited. In this study, we introduce a novel self-catalyzing curing agent, 4-(7-amino-1-naphthoxy) phthalonitrile (ANP), which functions both as a precursor and curing agent. The presence of amino and naphthoxy groups promotes efficient curing without the need for external catalysts, thereby expanding the processing window. Additionally, amino and cyano groups act as reactive sites and flexibilizers, enhancing the properties of bisphenol A-based PN (AFPN) resin systems. Thermal analysis revealed that the ANP-modified resin exhibits outstanding thermal and thermo-oxidative stability, with a 5% weight loss temperature (<i>T</i>_<i>5%</i>) exceeding 450&#xa0;°C and a glass transition temperature (<i>T</i>_<i>g</i>) above 439&#xa0;°C. Vector network analysis further demonstrated excellent dielectric properties, with a dielectric constant (<i>D</i>_<i>k</i>) of 3.15 and a dissipation factor (<i>D</i>_<i>f</i>) of 0.017 at 9.05&#xa0;GHz. These findings indicate that ANP effectively overcomes key limitations of conventional PN resins. As a multifunctional curing agent, ANP shows significant potential for the development of advanced PN-based composites in aerospace, electronic packaging, and microelectronic applications.</p> Graphical abstract <p></p>