<p>Microcrystalline cellulose has attracted significant interest for its broad range of applications owing to its exceptional physical characteristics and impressive biological properties, including biodegradability, biocompatibility and non-toxicity. This study investigates the effective use of underutilized <i>Cissus quadrangularis</i> stems, commonly known as bone setters, to isolate microcrystalline cellulose. The successful isolation of this microcrystalline cellulose from <i>Cissus quadrangularis</i> stem was achieved through a series of treatments involving alkali, bleaching and acid hydrolysis. These chemical treatments led to an increase in the crystallinity of cellulose as indicated by X-ray diffraction analysis, highlighting the presence of both amorphous and crystalline contents of cellulose. The rod-like shape of the isolated cellulose with a diameter measuring from 0.6 to 1.2&#xa0;μm, was evident from scanning electron microscopy. The Fourier transform infrared spectra indicated the complete elimination of non-cellulosic components present in the CQ biomass. UV-vis and photoluminescence analyses were employed to assess the optical characteristics of the microcrystalline cellulose. The isolated microcrystalline cellulose was employed as a catalyst for the degradation of Congo red and methylene blue dyes. The degradation efficiency was determined to be 87.7% and 88.7%, respectively, and was observed to follow pseudo first-order kinetics. The biocompatibility of microcrystalline cellulose was evaluated through in vitro assay using the HepG2 liver cancer cell line, demonstrating remarkable cytotoxicity with an IC₅₀ value of 31.2&#xa0;µg/ml. The findings suggest that microcrystalline cellulose derived from CQ biomass holds promise as a sustainable material with versatile applications, including biomedical and wastewater treatment.</p>