The field of functional nanohybrid material is an emerging research area in material science due to its vast range of applications. The use of novel technology and innovative therapeutics has led to potent applications, including controlling the size of nanoparticles (NPs). This has resulted in a novel report on the synthesis of manganese oxide NPs using aerial parts of queen of roses Prunus dulcis (almond) leaves, seed, and seed oil (using Clevenger apparatus), which functions as a reducing agent. Manganese sulfate was used as a precursor in the synthesis process. The synthesized nanohybrid Mn3O4 NPs were studied using different characteristics techniques such as X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy‐dispersive X‐ray spectroscopy (EDX). The photoluminescence spectra display the blue emission ranging from 483.2 to 486.5 nm. The biosynthesized Mn3O4 NPs were tested for bactericidal activity and showed tremendous inhibition against gram‐positive and gram‐negative bacteria. The antioxidant activity of Mn3O4 NPs was enhanced using 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay, which revealed the higher activity of Mn3O4 NPs from P. dulcis leaf extract. In vitro cytotoxicity of hybrid Mn3O4 NPs was examined using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay against cervical cancer (HeLa cell line) with different concentrations. The results showed an IC50 value of 61.97 μg mL−1 for Mn3O4 NPs from P. dulcis leaf extract. In general, the phytosynthetic route with synergistic effect of nanohybrid demonstrated an interaction with cancer cells, highlighting a pioneering optimum approach in synthesis of Mn3O4 NPs from aerial parts of P. dulcis.