A novel azo dye was prepared by reacting the diazonium salt of 3-aminophenol with 8-hydroxyquinoline and subsequently used to prepare a series of Ni+2, Pd+2, Pt+4, and Cu+2 complexes. The ligand structure was characterized via1H-and 13C-nuclear magnetic resonance spectroscopy. The as-synthesized materials were characterized via Fourier-transform infrared, ultraviolet‒visible, and mass spectroscopy, as well as thermo gravimetry, differential scanning calorimetry, and elemental analysis. Conductivity, magnetic susceptibility, and the metal and chloride contents of the complexes were also determined. The ligand exhibited a trigonal geometry, whereas the Cu+2, Pd+2, Pt+4, and Ni+2 complexesexhibited tetrahedral, square planar, octahedral, and tetrahedral geometries, respectively. The complexes contained water within the coordination field and all of them were non-electrolytes. The effectiveness of the ligand and metal complexes in inhibiting free radicals was evaluated by analyzing their antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl as the free radical and gallic acid as the standard. The ligand exhibited a higher ability to inhibit free radicals than the complexes based their IC50 values. The free radical scavenging ability was in the order of: (H2L > gallic acid > Cu+2 > Ni+2 > Pt+4 complex. The Pt+4 and Cu+2 complexes were evaluated as anticancer agents against theMCF-7cells using different concentrations (7.4, 22.22, 66.66, 200, and 600 μg/mL). The Pt+4 complex exhibited a lower IC50 value (147.61 μg/mL) than the Cu(II) complex(152.91 μg/mL), indicating its higher inhibition ability.