Nanotechnology offers promising opportunities in combating infectious agents, especially multidrug-resistant bacteria (MDR), which is a major concern in modern times. Zinc oxide nanoparticles (ZnO-NPs) are effective in delivering therapeutic agents to living systems due to their biocompatibility and bioactivity, making them effective against infectious microbes and also allowing them to be applied as an effective anticancer instrument. This study aimed to investigate the antimicrobial activity of ZnO-NPs against P. aeruginosa, a multi-drug resistant (MDR) bacterium in combination with Piperacillin-Tazobactam, as well as the in vitro effect of anticancer activity on MCF-7 and HepG2 cell lines. Piperacillin-Tazobactam, are beta-lactam antibiotics highly effective against Gram-positive and Gram-negative bacteria such as Pseudomonas aeruginosa, and recommended for the empirical treatment of Febrile Neutropenia (FN) after chemotherapy. ZnO-NPs of variable size (designated as ZnO-NPs-A, ZnO-NPs-B, and ZnO-NPs-C with 35±2.5 nm, 50±2 nm, and 65±3 nm mean sizes, respectively) and Piperacillin-Tazobactam alone and in combination were used for the study. The extended-spectrum beta-lactamase (ESBLs) producing MDR P. aeruginosa strain sensitivity profiling towards different combinations of ZnO-NPs and Piperacillin-Tazobactam was measured. There was no synergistic effect observed against growth inhibition of P. aeruginosa. The combined dose of ZnO-NPs-A and Piperacillin-Tazobactam showed great antibacterial efficacy even as compared to the pure drug against P. aeruginosa. Similarly, the Piperacillin-Tazobactam with ZnO-NPs-C showed the least cell viability as compared to the drug alone. The study showed a significant decrease in cell viability with the combined application of Piperacillin-Tazobactam and ZnO-Nps in comparison to the individual treatments.