A phthalonitrile-containing monomer derived from a plant oil (anethole) has been successfully synthesized by a facile two-step reaction in an overall yield of 84%. Upon high temperature, this monomer is converted to a cured phthalocyanine resin in the presence of a catalyst, 4,4′-bis(3-aminophenoxy)diphenyl sulfone (m-BAPS). Such a cured resin displays good thermostability including high glass transition temperature (Tg > 450 °C), low thermal expansion coefficient (CTE, near 62.99 ppm °C−1 from 25 to 400 °C) and high char yield (>72% at 1000 °C). These data are comparable to those of the most of the common phthalocyanine resins derived from the fossil resource, suggesting that the phthalonitrile-containing monomer is a suitable precursor for the preparation of the ablation-resistant materials used on the surface of the spacecrafts.