Gold nanoparticles (Au-NPs) were synthesized at room temperature using Prunus domestica (plum) fruit extract as reducing agent. The UV-visible absorption spectrum showed a characteristic optical absorption peak of Au-NPs at 543 nm. The X-ray diffraction pattern suggested the formation and crystallinity of Au-NPs. Spherical Au-NPs synthesized with an average particle size of 20 +/- 6 nm were confirmed by transmission electron microscopy. Fourier transform infrared spectroscopy analysis supported the role of water-soluble polyols and amino acids of plum fruit extract for bioreduction and stabilization of Au-NPs. The catalytic activity of Au-NPs was investigated for 4-nitrophenol (4-NP) reduction using UV-visible absorption spectroscopy. Biosynthesized Au-NPs showed a dose-dependent catalytic activity. Catalytic reduction followed pseudo-first-order kinetics with respect to 4-NP.