In this study, nanoparticles (Ag, Cu and Ag–Cu) were synthesized from Blighia sapida through an ecofriendly biological approach. The study characterized and comparatively investigated the antibacterial potential of the nanoparticles (NPs) on pharmaceutical wastewater-isolated bacteria. The toxicological implications due to wastewater treatment with the NPs were also investigated on liver and kidney function indices of Wistar rats. The synthesized NPs were revealed to be un-agglomerated spheres (Transmission Electron Microscopy), with hydrodynamic diameter between 70 and 90 nm and an overall surface zeta potential of – 28 to – 31 mV (Dynamic Light Scattering). Judging by the zone of inhibitions, minimum inhibitory concentrations and the minimum bactericidal concentrations values obtained in this study, the NPs could be said to have potentiated significant antibacterial effects with the most profound effect observed with the Ag–Cu NPs relative to Ag- and Cu NPs at 50 µg/ml. For the sub-acute toxicity evaluation, the NPs at 200 µg/kg showed signals of progressive onset of toxicity, marked by reduction in alkaline phosphatase, aspartate transaminase and gamma glutamyl transaminase activities in the liver and kidney of the NPs-treated groups (p > 0.05) compared to the control group. This result suggested that the synthesized NPs may not be safe for direct application at 200 µg/kg, and it is therefore recommended that safety precautions be adhered in the use of silver and copper nanoparticles.Graphical abstract: