The study investigates the therapeutic potential of the methanolic extract of Alternanthera sessilis (ASLE-M) through extensive phytochemical screening and various biological assays. ASLE-M was found to contain a wide array of bioactive compounds, including alkaloids, saponins, sterols, phenols, carbohydrates, tannins, flavonoids, fatty acids, terpenoids, and glycosides, indicating its diverse pharmacological properties. The reducing power assay demonstrated strong antioxidant activity, with ASLE-M effectively scavenging reactive oxygen species (ROS) and mitigating oxidative stress. Cytokine profiling revealed significant inhibition of key pro-inflammatory cytokines (IL-6, IL-1β, and TNF-α) in RAW264.7 cells, highlighting ASLE-M's potent anti-inflammatory effects. Additionally, ASLE-M exhibited notable neuroprotective properties by reducing ROS levels in SK-N-SH neuronal cells, thereby enhancing cellular antioxidant defenses and supporting neuronal health. These findings suggest that ASLE-M could be a valuable source of natural compounds for developing treatments against oxidative stress, inflammation, and neurodegenerative diseases. The study underscores the need for further in vivo studies and clinical trials to fully elucidate the therapeutic mechanisms and validate the efficacy of ASLE-M in various medical applications, particularly in managing inflammatory conditions and neurodegenerative disorders.