Alzheimer’s disease (AD), an aging-related disease, is characterized by chronic neuroinflammation and microglial activation, leading to neuronal death. Targeting the NOD-like receptors family pyrin domain containing 3 (NLRP3) inflammasome may offer therapeutic benefits. Through extensive screening of a natural herbal library using lipopolysaccharide/nigericin-stimulated BV-2 microglial cells, we discovered that Oenothera biennis, a plant-based functional food, significantly enhanced cell survival and inhibited the NLRP3 inflammasome. This was achieved by downregulating its component proteins and suppressing pyroptosis. Similar protective effects were observed in amyloid β (Aβ) 1–42-stimulated BV-2 cells, where O. biennis water extract (OWE) reduced inflammasome activity and modulated microglial phagocytic function. Additionally, OWE protected neuronal PC12 cells from inflammatory damage, underscoring its neuroprotective potential. Further mechanistic studies revealed that OWE activated autophagy by regulating the AMP-activated protein kinase-phosphoinositide 3-kinase/v-akt murine thymoma viral oncogene homolog/mammalian target of rapamycin (AMPK-PI3K/AKT/mTOR) signaling pathway. The effects of OWE on NLRP3 inflammasome inhibition and pyroptosis were reversed by treatment with bafilomycin A1 and compound C, indicating that autophagy plays a key role in these processes. In vivo studies showed that OWE activated autophagy and ameliorated Aβ-induced paralysis and death in Caenorhabditis elegans. Furthermore, OWE demonstrated neuroprotective effects in 3xTg-AD mice by improving cognitive functions and reducing inflammatory markers through autophagy induction. Collectively, our findings suggest that OWE, as a plant-based functional food, inhibits the activation of the NLRP3 inflammasome in microglia via AMPK-PI3K/AKT/mTOR-mediated autophagy, providing a promising therapeutic avenue for AD.