<p>Green synthesis represents an environmentally benign and sustainable strategy for producing nanomaterials with enhanced biological functionality and reduced toxicity. Niobium has shown great potential as a biomaterial under physiological conditions. This study aimed to investigate the use of natural antioxidants, ascorbic acid (AA), tannic acid (TA), and quercetin (QUE), as eco-friendly reducing and stabilizing agents in the green synthesis of niobium-based nanomaterials (Nb_nano). The obtained nanomaterials were characterized by UV-Vis spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning-transmission electron microscopy (STEM), scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM-EDX), and zeta potential analysis, indicating the formation of hydrated niobium pentoxide (Nb₂O₅·<i>n</i>H₂O) nanomaterials with well-preserved structural organization and morphology. Acute cytotoxicity assays using VERO-CCL81 cells revealed that antioxidant-mediated synthesis significantly reduced the toxic effects of Nb_nano, increasing their cytocompatibility. All nanomaterials exhibited antibiofilm activity against <i>Escherichia coli</i>, effectively reducing bacterial adhesion and biofilm formation. Except for AA-mediated Nb_nano, the systems also demonstrated bactericidal activity, revealing their dual action against planktonic and sessile bacterial forms. Overall, the green synthesis of niobium nanomaterials using natural antioxidants represents a sustainable and effective strategy for developing multifunctional materials with promising antibacterial and antibiofilm performance, coupled with reduced cytotoxicity. These findings highlight the potential of niobium-based nanomaterials for biomedical and antifouling applications.</p> Graphical Abstract <p></p>