The present study was based on green protocols for synthesizing cobalt sulfide nanoparticles using saffron stigma flower extract (Crocus sativus), as saffron is considered a potent traditional medicine. Furthermore, the novel cobalt sulfide (CoS) nanoparticles prepared by the green approach for the first time with saffron improved showed cytotoxicity and antibacterial activity, as well as significant antitumor activity of Hela, A549, and MCF 7 cells viz in vitro studies. The saffron-cobalt sulfide nanoparticles underwent characterization using various techniques which include the X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Advances in scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM), and the energy dispersive X-ray analysis spectroscopy. Both XRD, and FTIR confirmed the synthesis of pure cobalt sulfide nanoparticles. The resulting saffron-based cobalt sulfide nanoparticles exhibited a nanosphere structure, as confirmed by HRTEM, indicating the formation of nanosphere and microstructures. In vitro studies were conducted to assess the cytotoxicity and cell viability of Hela cells, A549, and MCF-7 cells. And, antibacterial studies were performed against various bacterial strains using different concentrations of cobalt sulfide nanoparticles derived from the red stigma of saffron (Crocus sativus) only the red stigma extract. The MTT assay analysis, cell viability, and morphological studies demonstrated the cytotoxic studies of the synthesized cobalt sulfide nanoparticles on cancer cells. The antibacterial test of the nanoparticles was also evaluated, revealing significant zones of inhibition (mm) against pathogens and cobalt sulfide nanoparticles using saffron extract, showcasing their potent cytotoxic, antibacterial, and antitumor activities with promising biomedical applications.