Herein, we report the development of a poly(amidoamine) (PAMAM) dendrimer based multicomponent therapeutic agent for in vitro cancer therapy applications. In this approach, Generation 5 (G5) PAMAM dendrimers stabilizing silver nanoparticle surface (DsAgNPs) were used to encapsulate anticancer drug 5-fluorouracil (5-FU) to attain synergism in cancer cells. 5-FU loaded DsAg nanocomposites (5-FU@DsAgNCs) were characterized by UV-visible spectroscopy, transmission electron microscopy, X-ray diffraction, and nuclear magnetic resonance measurements. In vitro release studies certify the sustained release of 5-FU from nanocomposites. 5-FU@DsAgNCs were found to elicit a synergistic antiproliferative effect in A549 (human lung cancer) and MCF-7 (human breast cancer) cells with IC50 of 5 μg mL(-1) and 1.5 μg mL(-1), and combination index (CI) values of 0.242 and 0.178, respectively. Atomic absorption spectroscopic analyses indicated higher cellular uptake of Ag in MCF-7 than that in A549 cancer cells. Nuclear and morphological alterations, typical of apoptosis induction, were revealed by fluorescence and scanning electron microscopy imaging. An increment in reactive oxygen species (ROS) levels was measured; this indicated the induction of oxidative stress in both 5-FU@DsAgNC treated cell types. Taken together, the apoptotic effects of 5-FU@DsAgNC were more prominent in MCF-7 than in A549 cancer cells. Finally, gene expression studies suggested triggering of the p53 mediated caspase signalling gene cascade in 5-FU@DsAgNC treated cells. The strategy to use dendrimer technology to design multicomponent 5-FU@DsAgNCs is quite promising for simultaneous delivery of 5-FU and DsAgNPs to achieve synergistic anticancer effects.