The aim of the study was to synthesize doxorubicin (DOX)-functionalized gold nanoparticles (GNPs) by a green method and to evaluate their anticancer potential against human cancer cell lines. These GNPs were synthesized with a green chemistry method and characterized by ultraviolet (UV) spectrophotometry, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and Zetasizer measurements. Surface plasmon resonance studies showed a clear UV-Visible peak at 532 nm, suggesting the formation of GNPs. FT-IR and XRD were used to determine the surface characteristics (presence of phytoconstituents) and crystalline nature of GNPs, respectively. The TEM and Zetasizer studies revealed a particle size of 74.7 +/- 2.47 nm with a zeta potential of -19.13 +/- 0.2. The synthesized GNPs were loaded with DOX by simple incubation method and evaluated for particle size, zeta potential, FT-IR and XRD to confirm drug loading. An in vitro anticancer assay of DOX-loaded GNPs (D-GNPs) against human cancer cell lines showed variations in responsiveness to D-GNPs, with significant activity against breast, lung, and prostate cancer cell lines. However, no significant difference was found in the percent cell viability of cervical, liver, and pancreatic cancer cell lines between DOX and D-GNPs. The results of the in vitro anticancer assay of D-GNPs against human cancer cell lines supports their potential for in vivo applications in cancer treatments. (C) 2015 Elsevier Ltd. All rights reserved.