<p>Cashew leaves are plants with high nutritional, medicinal, and biological properties. Age greatly affects the physiological properties of leaves, and this could interfere with their phytoconstituents and biological activities. However, there is paucity of information on effects of age on the phytochemical contents and neuroprotective properties of cashew leaves. Hence, this study sought to compare the phenolic contents and neuroprotective properties of young and mature cashew leaves in aluminum chloride-induced toxicity in <i>Drosophila melanogaster</i> model. The total phenolic and flavonoid content of young and mature cashew leaves were evaluated in vitro. Polyphenolic constituents of the leaves were determined using HPLC–MS. Subsequently, flies were exposed to aluminum chloride (AlCl₃) and treated groups received young and mature cashew leaves supplemented diet for 7&#xa0;days. Survival and negative geotaxis analysis were carried out. Flies’ tissue homogenates were prepared; reactive oxygen species (ROS), thiobarbituric acid reactive species (TBARS), and total thiol levels and superoxide dismutase (SOD), catalase, acetylcholinesterase (AChE), and monoamine oxidase-like (MAO-like) activities were assessed. The young cashew leaves had significantly (<i>p</i> &lt; 0.05) higher phenolic composition than mature cashew leaves. AlCl₃ significantly (<i>p</i> &lt; 0.05) reduced survival and locomotor rates, total thiol level, SOD, and catalase activities, with simultaneous increase in ROS and TBARS levels and AChE and MAO-like activities. These observed impairments were ameliorated in flies treated with young and mature cashew leaves. However, young cashew leaves had better antioxidative and neuroprotective properties which could possibly be related to its higher phytoconstituents. Hence, young cashew leaves could offer better health promoting effects in oxidative stress related diseases like neurodegeneration.</p>