The present work deals with the development of a series of trifunctional, fully biobased, sustainable polybenzoxazine composites for diverse applications, viz., high-dielectric, antibacterial, and corrosion-resistant uses. Thymol-containing trifunctional phenol (TTP) and the corresponding benzoxazines were prepared, and the molecular structure was confirmed using different spectroscopic analyses. Cure behavior of TTP-benzoxazine resins was studied using differential scanning calorimetry. TTP and furfurylamine-based benzoxazine (TTP-ff) monomer was selected as binder matrix and was reinforced with chicken feather carbon (CFC) and cashew nut shell (cake/residue) carbon (CNSC). The value of dielectric constant of 15 wt % of CFC and CNSC separately filled poly(TTP-ff) composites possesses 8.69 and 8.91, respectively. It was also observed that the biobased benzoxazines exhibited substantial antibacterial activity, indicating their potential utility in materials requiring inherent resistance against microbial colonization. Also, the poly(TTP-od)-coated fabric exhibits the value of WIC of 163°, which is superhydrophobic in nature and possess the behavior of self-cleaning and water-repellent surfaces. The poly(TTP-ol) offers better protection of mild steel surfaces from corrosive environment. Flexural strength of polybenzoxazine and its composites were studied for mechanical stability. Results from different studies showed that the developed biobased polybenzoxazine composites in the present work exhibit good dielectric performance, antimicrobial activity, superhydrophobic behavior, and anticorrosion applications.