The development of artificial enzymes to mimic the properties of natural enzymes has been receiving much research interest. Herein, zwitterionic dendrimer-encapsulated palladium nanoparticles (Pd_n-G5MC NPs) were constructed to investigate their biocompatibility and catalytic ability in bacterial solution. Zwitterionic dendrimer templates were synthesized via the surface modification of generation 5 polyamidoamine (G5 PAMAM) dendrimers with maleic anhydride and cysteamine. The Pd_n-G5MC NPs were prepared by incubation of the templates with disodium tetrachloropalladate, followed by reduction with sodium borohydride. The Pd_n-G5MC NPs displayed high stability, biocompatibility, and catalytic efficiency. Remarkably, Pd₅₅-G5MC NPs maintained high stability over a broad pH range (4–9) and high salt concentration (up to 20%) within 24 h. Pd₅₅-G5MC NPs did not show noticeable cytotoxicity to HUVEC cells or HeLa cells at a concentration of 500 μg mL⁻¹, while G5 PAMAM dendrimer-encapsulated palladium nanoparticles (Pd₅₅-G5 NPs) had obvious cytotoxicity (∼10% cell viability). Furthermore, Pd₅₅-G5 NPs had a minimal inhibitory concentration (MIC) of 400 μg mL⁻¹, while Pd_n-G5MC NPs did not show any bacterial growth inhibition at the same concentration. More importantly, Pd₅₅-G5MC NPs maintained their catalytic activity in bacterial solution compared to Pd₅₅-G5 NPs. The apparent rate constant k_app is dependent on the concentration of morin or hydrogen peroxide. All the forementioned properties suggested that Pd_n-G5MC NPs could be employed in bio-related systems in nature.