The synthesis of ZnMgO2 bimetallic oxide nanoparticles using Cinchona succirubra (C. succirubra) leaf extract was a focal point in the current study. Analyses through XRD, FTIR, SEM, TEM, and EDX validated the composition and formation of these nanoparticles, characterized by an average diameter of 23±1 nm. The significant positive impact on rice growth, in comparison to the control (water), underscored the remarkable effectiveness of this nanoparticle composition in promoting the growth activity of rice plants. Interestingly, as the duration extended from 20 to 60 days, the effect of conventional fertilizer (urea) remained constant, while ZnMgO2 NPs continued to enhance the plant's growth activity, including morphological and biochemical parameters. This extended nutrient release over a 40–50-day period, a notable contrast to the 4–10 days offered by conventional fertilizers (urea), further highlighted the advantageous feature of utilizing nanoparticles as fertilizers. This prolonged-release ensures sustained support for plant growth activities, contributing to long-term agricultural sustainability crucial for global food security. Moreover, the study observed significant stimulation of growth in seed germination, root and shoot length, α-Amylase activities, total phenol flavonoid contents, and total antioxidant activity at concentrations of 25 mg/L and 75 mg/L. This robust evidence strongly supports the efficacy of ZnMgO2 NPs. In conclusion, the results affirm that C. succirubra synthesized ZnMgO2 nanoparticles exert a considerable influence on morphological and biochemical parameters in rice seedlings, emphasizing their potential as a valuable component in agricultural practices.