Developing novel natural fiber thermoplastic composites is twofold effective. The Added-value of local agricultural wastes is enhanced and the environmental burden is reduced by less use of imported synthetic fibers and more recycling of agricultural waste. Material selection, parametric optimization, and characterization of biodegradable natural fiber thermoplastic composites with flame retardant properties are carried out in this work. Thermoplastic matrix is linear aliphatic low-density Polyethylene PE. [0–30 wt%] natural fibers of locally produced jute, corn silk, and Bagasse are used for reinforcing. Fibers are cut to different lengths after being alkali-treated. 16–24 % ammonium polyphosphate APP is used for fire retarding at different loadings. A coupling agent is added to link the polymer matrix with the fiber. 3% Ferric Stearate is used for biodegradability activation. The samples are produced using a compounding kneader at 180 °C. Mechanical, water absorption, and flame-retardant properties are characterized. The biodegradability index, which is an indication to what extent the products manufactured from the composite are eco-friendly, is being measured. Jute composites show the highest mechanical properties of 11 MPa ultimate strength and 8 GPa modulus of elasticity, whereas the corn silk composites have better performance of V-2 according to the UL94 flame retardancy test. Water absorption of 15% fiber content is reduced to 1%.