The present study aims to probe the antioxidative and anticancer activities of gold nanoparticles (AuNPs) reduced by Allium cepa L. (onion-O) and Allium sativum L. (garlic-G) extracts. Versatile analyzes were employed to evaluate the morphological and hydrodynamic properties of the particles, as well as to determine their bioactive components and radical scavenging activities. The biological effects of particles such as toxicity, proliferation, motility, and cell-death mechanism were tested in vitro on fibroblast (L929) and different cancer cell lines. The size range of the spherical particles prepared in three groups for each plant extract was found to vary between 5-10 nm and 7–18 nm for garlic and onion respectively, depending on the extract amount. The particles were also found to be well-dispersed and colloidally stable in aqueous media. Gallic acid was the common phenolic compound in the extracts. The radical scavenging properties of the particles increased depending on the extract amount, and the effect was greater in those synthesized with onion extract. When comparing different types of AuNPs, garlic-reduced AuNPs (GAuNPs) had a more stable effect on cancer cells than onion-reduced AuNPs (OAuNPs). Fluorescence staining showed that nanoparticles caused relatively similar necrotic responses in WiDr cells. However, OAuNPs triggered apoptosis to a greater extent in MCF-7 cells than GAuNPs. Both types of particles inhibited cell migration in both healthy and cancerous cells. In sum, both AuNPs exhibited cytotoxicity through their ability to modulate proliferation, apoptosis, and motility.