Functional foods are prospective in improving memory decline caused by Alzheimer’s disease and aging. The Edible seaweed Hizikia fusiforme functional oil (HFFO) inhibited acetylcholinesterase, prevented cellular neuroinflammation, and improved memory deficits in zebrafish models in the previous studies. To realize its greener preparation and lipid oxidation mitigation and study its effects on higher animals, more investigations are necessary. Herein, sub-critical fluid extraction of HFFO and successive complex coacervation embedding yielded a water-soluble and anti-oxidative microcapsule HFFOM, which displayed in vivo memory-improving effects on LPS-injured zebrafish and normal rodents in different behavior tests. HFFOM can elevate the level of the neurotransmitter acetylcholine while decreasing the levels of MDA, IL-1β, and TNF-α in the zebrafish brain. LC-MS/MS and lipidomic analysis suggested its predominant memory-improving ingredients to be linolenic, erucic, nervonic, arachidonic, linoleic, eicosatrienoic, docosahexaenoic, and docosapentaenoic acids. This study enlightens the potential of HFFOM in developing memory-enhancing functional foods or drugs.