<p>As nanotechnology advances and gets more integrated into several scientific domains, advantages are currently achieved. This is mainly due to the unique properties of nanoparticles (NPs) and the originality they bring to these applications. Particularly analytical chemistry, environmental sciences, and medicine. Nanotechnology has become one of the most interesting and advanced areas of research in this field. In the current work, the Au-NPs were synthesized using <i>Spirulina platensis</i>, as it holds qualities that can reduce inflammation and act as an antioxidant and also has a rich source of different types of proteins. The characterization process included UV-visible spectroscopy, XRD, FTIR, SEM, and TEM. The two cancer cell lines HepG-2 and A549 used for anticancer activity as well as DPPH, reducing power, total antioxidant capacity, and antibacterial activity in contradiction to many strains, were determined. Results indicated that the viability of the HepG2 and A549 tumor cell lines was around 92% and 87%, respectively, when exposed to a concentration of 100 µg of Au-NPs. However, at a concentration of 300 µg ml⁻¹, the Au-NPs showed huge toxicity, and the viability reached 31.45% for HepG2 and about 20.745% for A549. Similarly, the highest antioxidant activity was 70 ± 1.96 at a concentration of 300 µg ml⁻¹, and the lowest 40 ± 1.95 activity was recorded at a concentration of 50 µg ml⁻¹. 17 mm was the largest zone of inhibition that was shown against <i>Pseudomonas aeruginosa</i>. Several important properties of Au-NPs biosynthesized from <i>Spirulina platensis</i> were demonstrated, including their anti- antioxidant, and anticancer activity.</p> Graphical Abstract <p></p>