Tannic acid (TA) is one of the richly accessible and naturally occurring polyphenols that shows great potential as a green flame retardant (FR) material due to its intrinsic char-forming nature. Due to the increasing concern on the negative health effect of halogenated flame retardants and non-sustainable source of phosphorus-containing flame retardants, utilizing bio-derivatives is one of the emerging new approaches in the development of environment-friendly and sustainable flame retardants. However, the low thermal stability of TA limits its use as a melt-processable additive in polymers with high processing temperature (>230°C), such as Nylon. Nylon is one of the major engineering polymers with excellent mechanical properties and weathering resistance. It is currently used in protective clothing, electronics, automotive and various other applications. However, Nylon is a highly flammable material due to its melt dripping and non-charing behavior when exposed to the fire. In the present research, modified tannin-based thermally stable polyphenols were explored as char-forming additives or coatings for Nylon polymers. Upon thermal degradation, Nylon 6 blends containing 15% chemically modified tannin exhibit consistently lower peak heat release rate (pHRR) (52% reduction) and heat release capacity (HRC) (36% reduction) combined with enhanced char yield (9%). Modified tannin can also be utilized directly for coating applications. Nylon 66 fabric coated with a thin layer of modified tannin exhibited self-extinguishing behavior and char length less than 3 inches (76 mm) in modified vertical flame test. This research indicates that chemical modification of natural polyphenols can significantly improve overall thermal properties. In the presentation, we discuss how these materials could open up a new path for bio-derived polyphenol-based char forming materials for FR fiber/fabric coatings and plastics additives applications.