Nanozymes, which possess enzyme-like catalytic activity, are attractive alternatives to natural enzymes. Their activity is largely dependent on the structure of the material. However, challenges remain in optimizing the structure–activity relationship. This work explores the synthesis and utilization of PtCu nanostructures (NSs), focusing on their peroxidase (POD)-like properties and their potential as antibacterial agents. We developed PtCu dendrites that transform into unique dendroframe octahedrons (DFOs) and subsequently stabilize into solid octahedrons with unusual growth behaviour. The intermediate DFO, showed higher POD-like activity in comparison to other shapes of PtCu NSs. The DFOs also have the better ability to consume glutathione, thus enhancing their sterilization effect. Furthermore, we demonstrate the effectiveness of these PtCu DFOs as powerful antibacterial agents. This work provides valuable information on shape dependent activities of PtCu NSs in the field of biomedicine.