To alleviate the environmental hazard and minimize the practice of utilizing fossil fuel‐based precursors in the production of benzoxazines, sustainable bio‐phenol precursors namely magnolol and bio‐based amine furan‐2yl‐methanamine have been utilized to synthesize bio‐benzoxazine and was cured and characterized. The curing temperature of the synthesized bio‐benzoxazine monomer was found to be 216°C. Utilizing the carbon obtained from two different bio‐sources namely, chicken feather and cashew nut shell cake bio‐polybenzoxazine composites were prepared. The char yield of bio‐carbon reinforced bio‐polybenzoxazine composites was enhanced to 65% compared to that of neat polybenzoxazine (60%). The value of the dielectric constant of neat polybenzoxazine was found to be 5.52 which was further improved to a maximum of 8.9 and 7.8 on reinforcement of 15 wt% chicken feather carbon and 15 wt% cashew nut shell cake carbon respectively. The prepared bio‐polybenzoxazine composites exhibit a near superhydrophobic nature with the value of water repulsive angle at 150° than that of neat matrix (143°). From the obtained results, it is suggested that the sustainable bio‐carbon reinforced bio‐based benzoxazine will be a promising material for thermally stable, high dielectric, and water‐repellent applications.