Although flame retardants are very effective in reducing the fire hazard of polymeric materials, their presence may be detrimental to mechanical strength. Hence, in order to have a holistic improvement of performance properties, a new approach has been developed wherein biochar is used to host a naturally-occurring flame retardant (lanosol). The issue of loss in mechanical strength of a polymer host is alleviated by the use of biochar. Three different doping procedures were investigated, namely, dry mixing, and chemical and thermal-based doping, to integrate lanosol into the biochar pores. The doped biochar was used to develop wheat gluten-based blends. The mechanical and flammability properties of the blends were assessed. It was found that thermal doping was the most effective in introducing significant amounts of lanosol particles inside the biochar pores. The bioplastic containing chemically, and thermally doped biochar had equal tensile strength (5.2 MPa), which was comparable to that of the unmodified material (5.4 MPa). The thermally doped biochar displayed the lowest cone calorimeter peak heat release rate (636 kW m−2) for combustion and the highest apparent activation energy (32.4 kJ mol−1) for decomposition. Thus, for flame retarding protein-based matrices, the use of additives thermally doped into biochar is recommended to both simultaneously improve fire-resistance and conserve mechanical strength.