Natural rubber (RSS1 grade) reinforced with silica derived from bamboo leaves ash (BLA) was developed as a sustainable biocomposite material. The biosilica was obtained through controlled calcination of bamboo leaves followed by purification to yield predominantly amorphous SiO₂. Composites containing varying filler loadings were prepared through two roll mill mixing and subsequent vulcanization. Structural interactions between the rubber matrix and bio-silica were investigated using Fourier Transform Infrared (FTIR) spectroscopy. FTIR spectra revealed characteristic absorption bands of cis-1,4-polyisoprene along with Si–O–Si stretching vibrations, confirming thesuccessful incorporation of silica without altering the fundamental structure of the rubber backbone. Thermogravimetric analysis (TGA) demonstrated improved thermal stability and increased char residue with increasing biosilica content, attributed to the barrier effect and restricted polymer chain mobility. The results indicate that bamboo leaf–derived silica can act as an effective eco-friendly reinforcing filler for RSS1 rubber, enhancing thermal resistance while supporting sustainable material development.