Over the years, metal oxides have been leveraged to create several intriguing novel antibacterial active materials such that while finding the ways and means to increase efficiency, rare earth elements are found to have often served as potential optical dopants such that an optimistic en route to achieve the same, branched Sm-doped CuO nano-lanceolates were synthesized employing a wet chemical approach. The samples were then annealed at three distinct temperatures, which were fixed to 300 °C, 400 °C, and 500 °C. The nano-lanceolates have crystallized in the monoclinic phase, according to the XRD analysis. The SEM image of Sm-doped CuO captured at a magnification of 2 μm reveals a branched morphology, with multiple nano-lanceolates stacked in a stem. TEM image reveals that the width of a typical nano-lanceolate attached to a stem and its tip are found to be 87 nm and 212 nm, respectively and the obtained EDS data validate that elements including Cu, Sm, and O are present in the doped sample. The UV-visible spectra of the annealed samples indicate that the sample annealed at 300 °C (1.43 eV) has a larger band gap than the other samples. The sample that was annealed at 400 °C has endured defect emissions that are more intense than those of other samples, according to the obtained PL spectra. In addition to these fascinating findings, the samples annealed at 300 °C, 400 °C and 500 °C exhibit a zone of inhibition of 23 mm & 24 mm, 11 mm & 12 mm and 12 mm & 11 mm, respectively for the two tested bacterial strains which authenticate that the 300 °C annealed Sm-doped CuO nano-lanceolate deactivates the two pathogenic bacteria more effectively compared to the other samples. As a consequence, the Sm-doped CuO nano-lanceolates at 300 °C could potentially be an effective alternative for antibacterial materials, particularly in biomedical applications