The present research study aimed for biosynthesis of selenium nanoparticles (SeNPs) using Saccharomyces cerevisiae (baker's yeast) as a sustainable, green, ecofriendly and economically suitable source. The yeast mediated SeNPs were characterized to detect their physico-chemical properties by using UV–vis, TEM, DLS, FTIR and XRD analyses. The biosynthesized SeNPs were spherical in shape with size ranging from 34 to 125 nm, carrying negative charge equals -22.4 mV and had amorphous nature. FTIR indicated that SeNPs were surrounded with bioactive proteins as reducing and capping agents produced by yeast cells. Various biological capacities of biosynthesized SeNPs were measured including cytotoxicity, antiradical, anti-inflammatory and antimicrobial activities. The cytotoxicity results showed that, the yeast mediated SeNPs are non-toxic particles with IC50 value above 300 µg/ml therefore they can be applied as a safe and green therapeutic agent. Antiradical assay revealed that SeNPs had scavenging ability of DPPH. In addition, anti-inflammatory test ensured capacity of SeNPs to inhibit nitric oxide released from macrophage cells due to induced inflammation. Both antiradical and anti-inflammatory action was shown at noncytotoxic SeNPs concentrations. Highest antiradical activity (63.26%) was shown at 150 µg/mL SeNPs and the highest anti-inflammatory action (41.34%) was observed at 100 µg/mL. Subsequently, yeast derived SeNPs are safe, alternative and sustainable agent that can be used as antiradical and anti-inflammatory drug at their noncytotoxic levels (1-300 µg/mL).