Background: Green synthesis of metal and metal oxide nanoparticles (NPs) using plant extract performs a significant role as it is a promising alternative to the conventional chemical method in nanotechnology. Aims: In this paper, we report an environmentally benign method for the synthesis of silver nanoparticles (AgNPs) and zinc oxide nanoparticles (ZnONPs) using leaf extract of Garcinia livingstonei, and their mitotic activities were investigated using the root tip of Cicer arietinum. Objectives: The as-prepared NPs were characterized by ultraviolet-visible spectroscopy, infrared spectroscopy (FT-IR), X-ray diffraction (XRD), atomic force microscopy (AFM), and high-resolution transmission electron microscopy (HR-TEM). Analysis of FT-IR spectrum revealed that certain functional groups behaved as reducing and stabilizing agents in the formation of nanostructures. The crystalline nature of the AgNPs and ZnONPs was confirmed by XRD analysis. The size and shape of the as-obtained materials were found using HR-TEM analysis and were in the range of 5–65 nm and 38–94 nm for AgNPs and ZnONPs, respectively. Further, the root cells of C. arietinum were treated with both AgNPs and ZnONPs in different concentrations (5, 25, 50, and 100 μg/ml) for 24 h at the interval of 3, 6, 12, and 24 h along with distilled water as control. Results: The study clearly indicated that the AgNPs and ZnONPs showed an inhibitory effect on the cell division in root tip cells and caused a decrease in their mitotic index (MI) values. The reduction in MI in AgNPs is more evident than that of ZnONPs when compared to control. Aberrations in chromosomal behavior such as micronucleus, sticky chromosomes, bridges, multipolar anaphase, laggard, and c-metaphase were also observed. Conclusion: From the results, it is evident that the percentage of MI is inversely proportional, and chromosomal aberrations (CAs) are directly proportional to the concentration and duration of exposure.