Objective: The use of nanoparticles (NPs) in cancer diagnosis and treatment is a rapidly developing area of nanotechnology. The main objective of this research work is to synthesize copper oxide (CuO) NPs and to investigate its vitro anticancer and antibacterial property. Methods: The CuO NPs were synthesized via a facile and cost‑effective precipitation method using cupric acetate (monohydrate) (CuAc2.2H2O), sodium hydroxide, and glacial acetic acid. By varying the pH of the precursor solution, the morphology, particle size, and reaction rate of the NPs could be well tailored. The prepared CuO NPs were characterized by X‑ray diffraction, ultraviolet‑visible spectroscopy, Fourier transform infrared analysis, and scanning electron microscopy. Results: The results revealed a well crystalline structure with leaf‑like morphology. By controlling the pH of the solution, particle size and morphology of the NPs are altered. The synthesized CuO NPs have been screened for its antibacterial potency against Gram‑positive (Methicillin‑resistant Staphylococcus aureus and Bacillus subtilis) and Gram‑negative (Salmonella Paratyphi, Klebsiella pneumonia, and Enterobacter aerogenes) bacterial strains. The as‑synthesized NPs were found to be remarkable in inhibiting pathogenic bacteria. The anticancer activity reveals the dose‑dependent influence of CuO NPs against human breast cancer cell line Michigan Cancer Foundation‑7 (MCF‑7). Conclusions: The results suggested that CuO NPs have a wide range of antibacterial applications which can be used to control the spread and infection of a variety of bacterial strains. The CuO NPs showed promising anticancer activity against human breast cancer cell line (MCF‑7). Overall, CuO NPs are an effective candidate for pharmaceutical, biomedical, and environmental applications.