A novel bio-based flame retardant was synthesized for poly(lactic acid) (PLA) by inclusion of hydroxyapatite and lignocellulose and characterized, then put into practice. Hydroxyapatite-modified lignocellulose was prepared via in-situ synthesis of hydroxyapatite in the presence of lignocellulose. The chemical structure and thermal degradation behavior of novel bio-based flame retardant (LHP) was characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis (TGA). This bio-based flame retardant was added to a PLA matrix, with and without ammonium polyphosphate (APP), in order to evaluate its flame retardancy. The obtained PLA composites were characterized by transmission electron microscopy, TGA and cone calorimeter tests. The cone calorimeter results confirmed that the combination of the bio-based flame retardant and conventional APP flame retardant enhanced flame resistamce of PLA. The results exhibited the efficiency of this combination on PLA flame retardancy at a specified ratio between the bio-based flame retardant and APP.